Earthquake, Volcano and Tsunami: The Ultimate Environment Destroyer

Bharat Mahendra Shah

Role No: 53

Group VI - Environment and Legal Order

Introduction :

The Researcher is researching on effect of Earthquake, Volcano and Tsunami. These are

the ultimate destroyer of the Natural Environment and Human Environment. We usually

think of the ground and the oceans are peaceful things. The ground lies quietly beneath our

feet, and the ocean laps gently against the shore. But forces deep within the Earth can

suddenly destroy that peacefulness. These forces cause violent shakings called earthquakes;

explosions of ash, gases, and hot rocks called volcanoes; and huge waves called tsunamis.

(i) Earthquake: The plates usually move very slowly. But sometimes large pieces of

the plates get caught. The plates keep trying to move, but these large blocks of rock

hold them back. The pressure and energy build up. Then, suddenly, the rocks give

way, releasing all that pressure and energy. The plates jerk forward, and the ground

shakes. Far above, on the surface, people feel an earthquake. In a small earthquake,

the ground shakes a little, causing some hanging objects to swing. Tree branches

sway, as if there were a gentle breeze. Some earthquakes are so small that we do not

notice them. But sometimes the shaking is so strong that buildings crumble, bridges

collapse, and large cracks open in the ground over large areas.

(ii) Volcano: A volcano occurs wherever magma from deep inside the Earth comes out

through a crack in the surface. Volcanoes usually happen near the edges of the

plates, where there are many cracks and thin spots where the magma can leak out.

When the magma pours onto the surface, it hardens, often piling up into a mountain.

Sometimes, the liquid rock flows peacefully out across the land. This is how many of

the active volcanoes on the Hawaiian Islands behave.

(iii) Tsunami: Tsunamis are huge waves caused by earthquakes or volcanoes. They used

to be called “tidal waves.” But the word “tidal” means something to do with the

ocean’s normal tides, and tsunamis have nothing to do with the tides. Tsunamis can

be as high as a football field is long. They are the largest waves in the world.

Research Methodology : Doctrinal Research

Hypothesis:

Earthquake, Volcano and Tsunami has significant effect on our natural and human

environment which causes huge damages to life and property.

Chapterisation:

Chapter 1: Introduction

Chapter 2: Concept

Chapter 2.1: Concept of Earthquake

Chapter 2.2: Concept of Volcano

Chapter 2.3: Concept of Tsunami

Chapter 3: Effects

Chapter 3.1: Effects of Earthquake

Chapter 3.1: Effects of Volcano

Chapter 3.1: Effects of Tsunami

Chapter 4: Safety Precautions

Chapter 4.1: Safety Precautions during earthquake

Chapter 4.2: Safety Precautions during volcanic eruptions

Chapter 4.3: Safety Precautions during Tsunami

Chapter 5: Legal Framework

Conclusion: Now a day’s Earthquake, Volcano and Tsunami are serious challenges

before the world. Because all countries concentrate on only development. Therefore due to

massive development and without environment management global warming is increasing

day by day. Then Human and Natural life are going danger. Now a days we are listening

about news that Earthquake, Volcano and Tsunami are happen in most of countries again

and again.

earthquake, trembling or shaking movement of the earth's surface. Most earthquakes are minor tremors. Larger earthquakes usually begin with slight tremors but rapidly take the form of one or more violent shocks, and end in vibrations of gradually diminishing force called aftershocks. The subterranean point of origin of an earthquake is called its focus; the point on the surface directly above the focus is the epicenter. The magnitude and intensity of an earthquake is determined by the use of scales, e.g., the moment magnitude scale, Richter scale, and the modified Mercalli scale.

Causes of EarthquakesMost earthquakes are causally related to compressional or tensional stresses built up at the margins of the huge moving lithospheric plates that make up the earth's surface (see lithosphere). The immediate cause of most shallow earthquakes is the sudden release of stress along a fault, or fracture in the earth's crust, resulting in movement of the opposing blocks of rock past one another. These movements cause vibrations to pass through and around the earth in wave form, just as ripples are generated when a pebble is dropped into water. Volcanic eruptions, rockfalls, landslides, and explosions can also cause a quake, but most of these are of only local extent. Shock waves from a powerful earthquake can trigger smaller earthquakes in a distant location hundreds of miles away if the geologic conditions are favorable.

See also plate tectonics.

Seismic WavesThere are several types of earthquake waves including P, or primary, waves, which are compressional and travel fastest; and S, or secondary, waves, which are transverse, i.e., they cause the earth to vibrate perpendicularly to the direction of their motion. Surface waves consist of several major types and are called L, or long, waves. Since the velocities of the P and S waves are affected by changes in the density and rigidity of the material through which they pass, the boundaries between the regions of the earth known as the crust, mantle, and core have been discerned by seismologists, scientists who deal with the analysis and interpretation of earthquake waves (see earth). Seismographs (see seismology) are used to record P, S, and L waves. The disappearance of S waves below depths of 1,800 mi (2,900 km) indicates that at least the outer part of the earth's core is liquid.

Damage Caused by EarthquakesThe effects of an earthquake are strongest in a broad zone surrounding the epicenter. Surface ground cracking associated with faults that reach the surface often occurs, with horizontal and vertical displacements of several yards common. Such movement does not have to occur during a major earthquake; slight periodic movements called fault creep can be accompanied by microearthquakes too small to be felt. The extent of earthquake vibration and subsequent damage to a region is partly dependent on characteristics of the ground. For example, earthquake vibrations last longer and are of greater wave amplitudes in unconsolidated surface material, such as poorly compacted fill or river deposits; bedrock areas receive fewer effects. The worst damage occurs in densely populated urban areas where structures are not built to withstand intense shaking. There, L waves can produce destructive vibrations in buildings and break water and gas lines, starting uncontrollable fires.

Damage and loss of life sustained during an earthquake result from falling structures and flying glass and objects. Flexible structures built on bedrock are generally more resistant to earthquake damage than rigid structures built on loose soil. In certain areas, an earthquake can trigger mudslides, which slip down mountain slopes and can bury habitations below. A submarine earthquake can cause a tsunami, a series of damaging waves that ripple outward from the earthquake epicenter and inundate coastal cities.

Major EarthquakesOn average about 1,000 earthquakes with intensities of 5.0 or greater are recorded each year. Great earthquakes (magnitude 8.0 or higher) occur once a year, major earthquakes (magnitude 7.0–7.9) occur 18 times a year, strong earthquakes (magnitude 6.0–6.9) 10 times a month, and moderate earthquakes (magnitude 5.0–5.9) more than twice a day. Because most of these occur under the ocean or in underpopulated areas, they pass unnoticed by all but seismologists. Moderate to strong earthquakes can cause more significant destruction if they occur closer to the earth's surface. Notable earthquakes have occurred at Lisbon, Portugal (1755); New Madrid, Mo. (1811 and 1812); Charleston, S.C. (1886); Assam, India (1897 and 1950); San Francisco (1906); Messina, Italy (1908); Gansu, China (1920); Tokyo, Japan (1923); Chile (1960); Iran (1962); S Alaska (1964); Managua, Nicaragua (1972); Guatemala (1976); Hebei, China (1976); Mexico (1985); Armenia (1988); Luzon, Philippines (1990); N Japan (1993); Kobe, Japan (1995); Izmit, Turkey (1999); central Taiwan (1999); Oaxaca state, Mexico (1999); Bam, Iran (2003); NW Sumatra, Indonesia (2004); Sichuan, China (2008); S Haiti (2010); Chile (2010); South Island, New Zealand (2010, 2011); and NE Japan (2011). The Lisbon, Chilean, Alaskan, Sumatran, and NE Japan earthquakes were accompanied by significant tsunamis.

Twelve of the twenty largest earthquakes in the United States have occurred in Alaska. Most of the largest in the continental United States have occurred in California or elsewhere along the Pacific Coast, but the three New Madrid earthquakes (1811–12) also were among the

largest continental events, as was the Charleston, S.C., earthquake (1886). On Good Friday 1964, one of the most severe North American earthquakes ever recorded struck near Anchorage, Alaska, measuring 8.4 to 8.6 in magnitude. Besides elevating some 70,000 sq mi (181,300 sq km) of land and devastating several cities, it generated a tsunami that caused damage as far south as California. Other recent earthquakes that have affected the United States include the Feb., 1971, movement of the San Fernando fault near Los Angeles. It rocked the area for 10 sec, thrust parts of mountains 8 ft (2.4 m) upward, killed 64 persons, and caused damage amounting to $500 million. In 1989, the Loma Prieta earthquake above Santa Cruz shook for 15 seconds at an magnitude of 7.1, killed 67 people, and toppled buildings and bridges. In Jan., 1994, an earthquake measuring 6.6 with its epicenter in N Los Angeles caused major damage to the city's infrastructure and left thousands homeless.

BibliographySee C. H. Scholz, The Mechanics of Earthquakes and Faulting (1991); C. Lomnitz, Fundamentals of Earthquake Prediction(1994); D. S. Brumbaugh, Earthquakes: Science and Society (1998); B. A. Bolt, Earthquakes (4th ed. 1999). See also bibliography under seismology.

The Columbia Electronic Encyclopedia® Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.www.cc.columbia.edu/cu/cup/

earthquakeSudden shaking of the ground caused by a disturbance deeper within the crust of the Earth. Most earthquakes occur when masses of rock straining against one another along fault lines suddenly fracture and slip. The Earth's major earthquakes occur mainly in belts coinciding with the margins of tectonic plates. These include the Circum-Pacific Belt, which affects New Zealand, New Guinea, Japan, the Aleutian Islands, Alaska, and the western coasts of North and South America; the Alpide Belt, which passes through the Mediterranean region eastward through Asia; oceanic ridges in the Arctic, Atlantic, and western Indian oceans; and the rift valleys of East Africa. The “size,” or magnitude, of earthquakes is usually expressed in terms of the Richter scale, which assigns levels from 1.0 or lower to 8.0 or higher. The largest quake ever recorded (Richter magnitude 9.5) occurred off the coast of Chile in 1960. The “strength” of an earthquake is rated in intensity scales such as the Mercalli scale, which assigns qualitative measures of damage to terrain and structures that range from “not felt” to “damage nearly total.” The most destructive quake of modern times occurred in 1976, when the city of Tangshan, China, was leveled and more than 250,000 people killed.

EARTHQUAKES

Earthquake is one of the most destructive natural hazard. They may occur at any time of the year, day or night, with sudden impact and little warning. They can destroy buildings and infrastructure in seconds, killing or injuring the inhabitants. Earthquakes not only destroy the entire habitation but may de-stabilize the government, economy and social structure of the country.

Earthquakes are the manifestations of sudden release of strain energy accumulated in the rocks over extensive periods of time in the upper part of the Earth.

Seismology (derived from Greek word Seismos meaning Earthquake and Logos meaning science) is the science of Earthquakes and related phenomena.

Seismograph/ Seismogram Seismograph is an instrument that records the ground motions. Seismogram is a continuous written record of an earthquake recorded by a seismograph.

Seismic Zonation Map of India

Seismic Zonation map of a country is a guide to the seismic status of a region and its susceptibility to earthquakes. India has been divided into five zones with respect to severity of earthquakes. Of these, Zone V is seismically the most active where earthquakes of magnitude 8 or more could occur recent strong motion observations around the world have revolutionized thinking on the design of engineering structures, placing emphasis also on the characteristics of the structures themselves it should be realized that in the case of shield type earthquakes, historic data are insufficient to define zones because recurrence intervals are much longer than the recorded human history this may often give a false sense of security. Occurrence of the damaging earthquake at Latur, falling in zone I is a typical example of this situation.

Cause of Earthquake :

The earth’s crust is a rocky layer of varying thickness ranging from a depth of about 10kilometers under the sea to 65 kilometers under the continents. The crust is not one piece but consists of portions called ‘plates’ which vary in size from a few hundred to thousands of kilometers. The ‘theory of plate tectonics’ holds that theplates ride up on the more mobile mantle,and are driven by some yet unconfirmed mechanisms, perhaps thermal convection currents. When these plates contact each other, stress arises in the crust. These stresses can be classified according to the type of movement along the plate’s boundaries:a) pulling away from each other,b) pushing against one another andc) sliding sideways relative to each other.

All these movements are associated with earthquakes.The areas of stress at plate boundaries which release accumulated energy by slipping or rupturing are known as 'faults'. The theory of 'elasticity' says that the crustis continuously stressed by the movement of the tectonic plates; it eventually reaches a point of maximum supportable strain. A rupture then occurs along the fault and the rock rebounds under its own elastic stresses until the strain is relieved. The fault rupture generates vibration called seismic (from the Greek 'seismos' meaning shock or earthquake) waves, which radiates from the focus in all directions. The point of rupture is called the 'focus' and may be located near the surface or deep below it. The point on the surface directly above the focus is termed as the  epicenter' of the earthquake

Magnitude:

It is a quantity to measure the size of an earthquake and is independent of the place of the observation.

Richter Scale:

The local magnitude is defined as the logarithm of the maximum amplitude measured in microns on a seismogram written by Wood-Anderson seismograph with free period of 0.8 second, magnification of 2,800, damping factor of 0.8 calculated to be at a distance of 100 kms. The relative size of events is calculated by comparison to a reference event of ML=0,using the formula, ML=log A-log Ao

        where A is the maximum trace amplitude in micrometer recorded on a standard seismograph and Ao is a standard value which is a function of epicentral distance (Δ) in kilometers.

Classification of earthquakesCategory Magnitude on Richter ScaleSlight Upto 4.9Moderate 5.0 to 6.9Great 7.0 to 7.9Very Great 8.0 and more

Source: www.imd.gov.inIndia has witnessed some of the most devastating earthquakes during the last century like the one in Kangra (1905), Bihar-Nepal (1934) and in Assam (1950). In the recent past, earthquakes have caused havoc in Uttarkashi (1991), Latur (1993), Jabalpur (1997), Chamoli (1999) and in Bhuj (2001). On 26th January 2001, India experienced one of the worst earthquakes in recent times. Measuring 6.9 on the Richter scale, the earthquake caused incalculable damage not just to its epicenter, Bhuj but also to other towns of the district of Kutch and to about 500 villages out of the total of 900 villages. The reported damage to property in Gujarat was about Rs.21, 000crore and the number of human lives lost were about 14,000. Of these, more than 500 deaths were reported from Ahmedabad, situated at a distance of about 350 kms from Bhuj. In the same city, close to 150 multi-storied buildings crumbled down. Cities far away from the epicenter, like Surat, too reported damage to property. 

SOME DAMAGING EARTHQUAKES IN INDIA AND APPROXIMATE NUMBER OF LIVES LOST

Year of occurrence

Place of occurrence Intensity   Others

1618 Bombay - - 2000 lives lost1720 Delhi 6.5 - Some lives lost1737 Bengal - - 300,000 lives lost

1803 Mathura 6.5 - The shock felt up to Calcutta.

1803 Kumaon 6.5 - Killed 200-300 people.

1819 Kutchch 8.0 XIChief towns of Tera, Kathara and Mothala razed to the ground.

1828 Srinagar 6.0 - 1000 people killed.1833 Bihar 7.7 X Hundreds of people killed1848 Mt.Abu, Rajasthan 6.0 - Few people killed

1869 Assam 7.5 - Affected an area of 2,50,000 Sq. miles.

1885 Srinagar 7.0 - Kamiarary area destroyed.1897 Shillong 8.7 XII Wide spread destruction in

Shillong.

1905 Himachal Pradesh 8.0 XI Thousands of people killed.

1906 Himachal Pradesh 7.0 - Heavy damage.

1916 Nepal 7.5 - All houses collapsed at Dharchulla.

1918 Assam 7.6 - Heavy damage.1930 Dhubri, Meghalaya 7.1 IX Heavy damage in Dhubri.1934 Bihar, Nepal 8.3 XI Large number of border

area people killed.1935 Quetta (in Pakistan) 7.5 IX 25,000 people killed1941 Andaman 8.1 X Very heavy damage.1947 Dibrugarh 7.8 - Heavy damage.

1950 Assam 8.6 XII Heavy damage to life and property.

1952 NE India 7.5 - Heavy damage.1956 Bulandshahar, U.P. 6.7 VIII Many people killed1956 Anjar, Gujarat 7.0 VIII Hundreds of people killed1958 Kapkote, U.P. 6.3 VIII Many people killed1967 Koyna, 6.1 VIII Koyna Nagar razed.1969 Bhadrachalam 6.5 1 Heavy damage.1986 Dharamshala (H.P) 5.7 VIII Lots of damage.1988 Assam 7.2 IX Few people killed

1988 Bihar- Nepal 6.5 VIII Large number of people killed.

1991 Uttarkashi 6.6 VIII Lots of damage to life and property.

1993 Latur 6.4 VIIIHeavy damage to life and property about, 000 people killed.

1997 Jabalpur 6.0 VIIILots of damage to property, about 39 lives lost.

1999 Chamoli 6.8 VIIILots of damage to property about 100 people lost lives.

2001 Bhuj 6.9 X Huge devastation, about ~ 14000 people lost lives

EARTHQUAKE HAZARDS IN INDIA

India has had a long history of earthquake occurrences. About 65% of the total area of the country is vulnerable to seismic damage of buildings in varying degrees. The most vulnerable areas, according to the present seismic zone map of India, are located in the Himalayan and sub-Himalayan regions, Kutch and the Andaman and Nicobar Islands. Depending on varying degrees of seism city, the entire country can be divided into the following seismic regions:

Kashmir and Western Himalayas - Covers the states of Jammu and Kashmir, Himachal Pradesh and sub-mountainous areas of Punjab

Central Himalayas - Includes the mountain and sub-mountain regions of Uttar Pradesh and the sub-mountainous parts of Punjab North-east India - Comprises the whole of Indian territory to the east of north Bengal Indo-Gangetic basin and Rajasthan - This region comprises of Rajasthan, plains of Punjab, Haryana, Uttar Pradesh and West

Bengal Cambay and Rann of Kutch Peninsular India, including the islands of Lakshwadeep The Andaman and Nicobar Islands

MEASURES FOR EARTHQUAKE RISK REDUCTION

For better understanding of all the possibilities of earthquake risk reduction, it is important to classify them in terms of the role that each one of them could play. Therefore, in the pre-earthquake phase, preparedness, mitigation and prevention are concepts to work on. Post-disaster,

immediate rescue and relief measures including temporary sheltering soon after an earthquake until about 3 months later and re-construction and re-habilitation measures for a period of about six months to three years need to follow. To encapsulate, the most effective measures of risk reduction are pre-disaster mitigation, preparedness and preventive measures to reduce vulnerability and expeditious, effective rescue and relief actions immediately after the occurrence of the earthquake. Depending upon the calamity and its consequences, strategies can also be divided into long term (five to fifteen years), medium term (one to five years) and short term (to be taken up immediately in high risk areas). Since it has been realized that earthquakes don't kill people but faulty constructed buildings do, the task of reducing vulnerability of structures and buildings will be the key to earthquake risk reduction. Also, pre-disaster preparedness through a post-earthquake response plan, including training of the concerned personnel in various roles, is considered essential for immediate and effective response after an earthquake occurrence. The major action points are highlighted in the following paragraphs. 

PRE-DISASTER PREVENTIVE MEASURES Long-term measures

Re-framing buildings' codes, guidelines, manuals and byelaws and their strict implementation. Tougher legislation for highly seismic areas.

Incorporating earthquake resistant features in all buildings at high-risk areas. Making all public utilities like water supply systems, communication networks, electricity lines etc. earthquake-proof. Creating

alternative arrangements to reduce damages to infrastructure facilities. Constructing earthquake-resistant community buildings and buildings (used to gather large groups during or after an earthquake)

like schools, dharamshalas, hospitals, prayer halls, etc., especially in seismic zones of moderate to higher intensities. Supporting R&D in various aspects of disaster mitigation, preparedness and prevention and post-disaster management. Evolving educational curricula in architecture and engineering institutions and technical training in polytechnics and schools to

include disaster related topics.

Medium term measures

Retrofitting of weak structures in highly seismic zones. Preparation of disaster related literature in local languages with dos and don'ts for construction. Getting communities involved in the process of disaster mitigation through education and awareness. Networking of local NGOs working in the area of disaster management.

Earthquake Facts & Statistics

Frequency of Occurrence of Earthquakes

Descriptor Magnitude Average Annually Great 8 and higher 1 ¹Major 7 - 7.9 17 ²Strong 6 - 6.9 134 ²Moderate 5 - 5.9 1319 ²Light 4 - 4.9 13,000 (estimated)Minor 3 - 3.9 130,000 (estimated)Very Minor 2 - 2.9 1,300,000 (estimated)¹Based on observations since 1900.² Based on observations since 1990.

Year-wise description of Earth Quakes

Number of Earthquakes Worldwide for 2000 - 2005. Located by the US Geological Survey National Earthquake Information CenterMagnitude 2000 2001 2002 2003 2004 20058.0 to 9.9 1 1 0 1 2 17.0 to 7.9 14 15 13 14 14 96.0 to 6.9 158 126 130 140 140 1165.0 to 5.9 1345 1243 1218 1203 1509 13074.0 to 4.9 8045 8084 8584 8462 10894 10264

3.0 to 3.9 4784 6151 7005 7624 7937 57822.0 to 2.9 3758 4162 6419 7727 6317 32491.0 to 1.9 1026 944 1137 2506 1344 200.1 to 0.9 5 1 10 134 103 0No Magnitude 3120 2938 2937 3608 2939 642 

Total 22256 23534 27454 31419 * 31199 * 21390 

Estimated Deaths 231 21357 1685 33819 284010 1957

List of Some Significant Earthquakes in India

Date Epicenter Location Magnitude1819 Jun 16 23.6 68.6 Kutch,Gujarat 8.01869 Jan 10 25 93 Near Cachar, Assam 7.51885 May 30 34.1 74.6 Sopor, J&K 7.01897 Jun 12 26 91 Shillongplateau 8.71905 Apr 04 32.3 76.3 Kangra, H.P 8.01918 Jul 08 24.5 91.0 Srimangal, Assam 7.61930 Jul 02 25.8 90.2 Dhubri, Assam 7.11934 Jan 15 26.6 86.8 Bihar-Nepalborder 8.31941 Jun 26 12.4 92.5 Andaman Islands 8.11943 Oct 23 26.8 94.0 Assam 7.21950 Aug 15 28.5 96.7 Arunachal Pradesh-China Border 8.51956 Jul 21 23.3 7.0 Anjar, Gujarat 7.01967 Dec 10 17.37 73.75 Koyna, Maharashtra 6.51975 Jan 19 32.38 78.49 Kinnaur, Hp 6.21988 Aug 06 25.13 95.15 Manipur-Myanmar Border 6.61988 Aug 21 26.72 86.63 Bihar-Nepal Border 6.41991 Oct 20 30.75 78.86 Uttarkashi, Up Hills 6.61993 Sep 30 18.07 76.62 Latur - Osmanabad, Maharashtra 6.31997 May 22 23.08 80.06 Jabalpur, MP 6.01999 Mar 29 30.41 79.42 Champoli, UP 6.82001 Jan 26 23.40 70.28 Bhuj, Gujarat 6.9

Extensive Definition

An earthquake is the result of a sudden release of energy in the Earth'scrust that creates seismic waves. Earthquakes are recorded with aseismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, or the related and mostly obsolete Richter magnitude, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modifiedMercalli scale.

At the Earth's surface, earthquakes manifest themselves by a shaking and sometimes displacement of the ground. When a large earthquakeepicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, huge amounts of gas migration, mainly methane deep within the earth, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.

An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter means the point at ground level directly above this.

Naturally occurring earthquakes

Tectonic earthquakes will occur anywhere within the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of transform or convergent type plate boundaries, which form the largest fault surfaces on earth, they will move past each other smoothly and aseismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance. Most boundaries do have such asperities and this leads to a form of stick-slip behaviour. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.

Earthquakes away from plate boundariesWhere plate boundaries occur within continental lithosphere, deformation is spread

out a over a much larger area than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace (e.g. the “Big bend” region). The Northridge earthquake was associated with movement on a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary between the Arabian and Eurasian plates where it runs through the northwestern part of the Zagros mountains. The deformation associated with this plate boundary is partitioned into nearly pure thrust sense movements perpendicular to the boundary over a wide zone to the southwest and nearly pure strike-slip motion along the Main Recent Fault close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms.

All tectonic plates have internal stress fields caused by their interactions with neighbouring plates and sedimentary loading or unloading (e.g. deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to intra-plate earthquakes.

Deep focus earthquakesThe majority of tectonic earthquakes originate at depths not exceeding tens of

kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquakes may occur at much greater depths (up to seven hundred kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. These are earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.

Earthquakes and volcanic activityEarthquakes also often occur in volcanic regions and are caused there, both by

tectonic faults and by the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions.

Earthquake stormsSometimes a series of earthquakes occur in a sort of earthquake storm, where the

earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar toaftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.

Size and frequency of occurrence

Minor earthquakes occur nearly constantly around the world in places like California and Alaska in the U.S., as well as in Chile, Peru, Indonesia,Iran, Pakistan the Azores in Portugal, Turkey, New Zealand, Greece,Italy, and Japan, Larger earthquakes occur less frequently, the relationship being exponential; for example, roughly ten times as many earthquakes larger than magnitude 4 occur in a particular time period than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are:

an earthquake of 3.7 - 4.6 every year an earthquake of 4.7 - 5.5 every 10 years an earthquake of 5.6 or larger every 100 years.

The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past because of the vast improvement in instrumentation (not because the number of earthquakes has increased). The USGSestimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0-7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable. In fact, in recent years, the number of major earthquakes per year has actually decreased, although this is likely a statistical fluctuation. More detailed statistics on the size and frequency of earthquakes is available from the USGS.

Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-km-long, horseshoe-shaped zone called the circum-Pacific seismic belt, also known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Massive earthquakes tend to occur along other plate boundaries, too, such as along the Himalayan Mountains.

With the rapid growth of mega-cities such as Mexico City, Tokyo orTehran, in areas of high seismic risk, some seismologists are warning that a single quake may claim the lives of up to 3 million people.

Effects/impacts of earthquakes

There are many effects of earthquakes including, but not limited to the following:

Shaking and ground ruptureShaking and ground rupture are the main effects created by earthquakes, principally

resulting in more or less severe damage to buildings or other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration.

Specific local geological, geomorphological, and geostructural features can induce high levels of shaking on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the seismic motion from hard deep soils to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical setting of the deposits.

Ground rupture is a visible breaking and displacement of the earth's surface along the trace of the fault, which may be of the order of few metres in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams, bridges and nuclear power stations and requires careful mapping of existing faults to identify any likely to break the ground surface within the life of the structure.

Landslides and avalanchesEarthquakes can cause landslides and avalanches, which may cause damage in hilly

and mountainous areas.

FiresFollowing an earthquake, fires can be generated by break of theelectrical power or

gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.

Soil liquefactionSoil liquefaction occurs when, because of the shaking, water-

saturatedgranular material temporarily loses its strength and transforms from asolid to a liquid. Soil liquefaction may cause rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits.

TsunamiUndersea earthquakes and earthquake-triggered landslides into the sea, can

cause Tsunami. See, for example, the 2004 Indian Ocean earthquake.

FloodsFloods may be a secondary effects of earthquakes, if dams are damaged.

Earthquakes may cause landslips to dam rivers, which then collapse and cause floods.

Human impactsEarthquakes may result in disease, lack of basic necessities, loss of life, higher

insurance premiums, general property damage, road and bridge damage, and collapse of buildings or destabilization of the base of buildings which may lead to collapse in future earthquakes.

The most significant human impact is loss of life

Preparation for earthquakes

Earthquake preparedness

Household seismic safety HurriQuake  nail (for resisting hurricanes and earthquakes) Seismic retrofit Seismic hazard Mitigation of seismic motion Earthquake prediction

Specific fault articles

Alpine Fault Calaveras Fault Cascadia subduction zone Geology of the Death Valley area Great Sumatran fault Hayward Fault Zone Hope Fault Liquiñe-Ofqui Fault North Anatolian Fault Zone New Madrid Fault Zone San Andreas Fault Wasatch Fault

Major earthquakes

Pre-20th century

Pompeii  (62 AD). Aleppo Earthquake  (1138). Basel earthquake  (1356). Major earthquake that struck Central Europe in 1356. Carniola  earthquake (1511). A major earthquake that shook a large portion of South-Central Europe. Its epicenter was around the town of Idrija, in today's Slovenia. It caused great damage to structures all over Carniola, including Ljubljana, and in westernCarinthia, particularly in Villach and Klagenfurt which were almost completely destroyed. There was some minor damage inVenice and other cities, too. Shaanxi Earthquake  (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China. Dover Straits  (1580). Dubrovnik earthquake  (1667). Disastrous earthquake inDubrovnik, Croatia killed about 3/5 of the population. Port Royal  Earthquake (1692). An earthquake on June 7, 1692, largely destroyed Port Royal, a safe harbor for pirates, causing two thirds of the city to sink into the Caribbean Sea. The great Sicilian earthquake  (1693). As many as 100,000 may have died. Cascadia Earthquake  (1700). Tokyo  earthquake (1703). 37,000 died. Kamchatka earthquakes  (1737) The third biggest earthquake on record measuring 9.3 on the Richter scale. Lisbon earthquake  (1755), one of the most destructive and deadly earthquakes in history, killing between 60,000 and 100,000 people and causing a major tsunami that affected parts of Europe,North Africa and the Caribbean.

Calabria earthquake  (1783). Series of 6 earthquakes in Calabria,Italy killed 50,000. Quito  earthquake. (1797) Quito, Viceroyalty of Peru, now the capital of Ecuador, was devastated by an earthquake. 40,000 died. New Madrid Earthquake  (1811), and another tremor (1812) that also struck the small Missouri town, was reportedly the strongest ever in North America and made the Mississippi Rivertemporarily change its direction and permanently altered its course in the region. Fort Tejon Earthquake  (1857). Estimated Richter Scale above 8, said the strongest earthquake in Southern California history. Great Neapolitan Earthquake  (1857). Estimated Richter Scale of 6.9. 11,000 dead. 1872 Lone Pine earthquake  (1872). Might been strongest ever measured in California with an estimated Richter Scale of 8.1 saidseismologists. Charleston earthquake  (1886). Largest earthquake in the southeastern United States, killed 100. Ljubljana earthquake  (14. IV. 1895), a series of powerful quakes that ultimately had a vital impact on the city of Ljubljana, being acatalyst of its urban renewal. Assam earthquake of 1897  (1897). Large earthquake that destroyed all masonry structures, measuring more than 8 on the Richter scale.

20th century

San Francisco Earthquake  (1906). Between 7.7 and 8.3 magnitudes; killed approximately 3,000 people and caused around $400 million in damage; most devastating earthquake in California and U.S. history. Messina Earthquake  (1908). Killed about 60,000 people. Gansu earthquake  (1920). Killed 200,000 in Gansu province,China. Great Kantō earthquake  (1923). On the Japanese island ofHonshū, killing over 140,000 in Tokyo and environs. 1931 Hawke's Bay earthquake . Occurred in the Hawkes Bay in theNorth Island of New Zealand leaving 256 dead. 1933 Long Beach earthquake 1935 Balochistan earthquake  at Quetta, Pakistan measuring 7.7 on the Richter scale. Anywhere from 30,000 to 60,000 people died 1939 Erzincan earthquake  at Erzincan, Turkey measuring 7.9 on the Richter scale. Ashgabat earthquake  (1948). Earthquake in Ashgabat, Soviet Union measuring 7.3 on the Richter scale killed over 110,000 (2/3 the population of the city). Assam earthquake of 1950  (1950). Earthquake in Assam, India measures 8.6M. Kamchatka earthquakes  (1952 and 1737), measuring >9.0. Great Kern County earthquake (1952). This was second strongest tremor in Southern California history, epicentered 60 miles North of Los Angeles. Major damage in Bakersfield, California and Kern County, California, while it shook the Los Angeles area. 1959 Yellowstone earthquake , formed Quake Lake in southern Montana, USA Great Chilean Earthquake  (1960). Strongest earthquake ever recorded, 9.5 on Moment magnitude scale, and generatedtsunamis throughout the Pacific ocean. It measured 9.6 on theRichter scale. 1960 Agadir earthquake , Morocco with around 15,000 casualties. 1963 Skopje earthquake , measuring 6.1 on the Richter scale kills 1,800 people, leaves another 120,000 homeless, and destroys 80% of the city.

Good Friday Earthquake  (1964) In Alaska, it was the fourth biggest earthquake recorded, Luzon Earthquake  (1990). On 16 July 1990, an earthquake measuring 7.7 on the Richter scale struck the island of Luzon, Philippines. Landers, California earthquake  (1992). Serious damage in the small town of Yucca Valley, California and was felt across 10 states in Western U.S. Another tremor measured 6.4 struck 3 hours later and felt across Southern California. August 1993  Guam Earthquake, measuring 8.2 on the Richter scale and lasting 60 seconds. 1993 Latur earthquake  Latur Earthquake,an earthquake of magnitude 6.3 on Richter Scale rocked the districts of Latur and Osmanabad in Maharashtra in India.The degree of fury was such that dwellings in several villages of these 2 districts were totally converted to debris. In adjoining Karnataka state, 9 people were killed and about 16,000 people injured. A huge number of houses were damaged. Northridge, California earthquake  (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction. Sakhalin earthquake  (1995). Measuring 7.6 on the Richter scale, killing over 2,000 people in Sakhalin, Russia. Great Hanshin earthquake  (1995). Killed over 6,400 people in and around Kobe, Japan. 1998 Afghanistan earthquake (1998). 6.9 on the Richter scale. Some 125 villages were damaged and 4000 people killed. Athens earthquake  (1999). 5.9 on the Richter scale, it hit Athenson September 7. Epicentered 10 miles north of the Greek capital, it claimed 143 lives. Chi-Chi earthquake  (1999) Also called the 921 earthquake. StruckTaiwan on September 21, 1999. Over 2,000 people killed, destroyed or damaged over ten thousand buildings. Caused world computer prices to rise sharply. Armenia, Colombia  (1999) 6.2 on the Richter scale, Killed over 2,000 in the Colombian Coffee Grown Zone. 1999 İzmit earthquake measuring 7.5 on the Richter scale and killed over 40,000 people and left approximately half a million people homeless in northwestern Turkey. Hector Mine earthquake  (1999). 7.1 on the Richter scale, epicentered 30 miles east of Barstow, California, widely felt in California and Nevada. 1999 Düzce earthquake at Düzce, Turkey measuring 7.2 on the Richter scale. Baku earthquake  (2000).

21st century

Nisqually Earthquake  (2001). El Salvador earthquakes  (2001). 7.9 (13 January) and 6.6 (13 February) magnitudes, killed more than 1,100 people. Gujarat Earthquake  (26 January 2001). Hindu Kush earthquakes  (2002). Over 1,100 killed. Molise earthquake  (2002) 26 killed. Bam Earthquake  (2003). Over 40,000 people are reported dead. Parkfield, California earthquake  (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures. Chūetsu earthquake  (2004).

Sumatra-Andaman Earthquake  (26 December 2004). By some estimates, the second largest earthquake in recorded history (estimates of magnitude vary between 9.1 September 2007 Sumatra earthquakes  8.0 magnitude September 12 (2007) November 14, 2007, 7.7 magnitude, Antofagasta, Chile  (2007). November 29, 2007, 7.4 magnitude, Caribbean Sea  (2007). December 20, 2007 6.8 magnitude, Gisborne, New Zealand (2007). February 20  2008 Sumatra earthquake 7.5 magnitude February 25  2008 Sumatra earthquake 7.3 magnitude. The quake was centered about 160 km (100 miles) south-southwest ofPadang. The Pacific Tsunami Warning Center issued a localtsunami watch. March 21  2008 China earthquake 7.2 magnitude. The quake happened in Yutian County, Xinjiang, a remote region in theKunlun Mountains far from any residential areas. March 29  2008 Sumatra earthquake 6.3 magnitude. The epicenter was about 175 miles (281 kilometers) south of Banda Aceh -- in a region hard-hit by the 2004 Indian Ocean earthquake. The Pacific Tsunami Warning Center issued warnings on the possibility of the quake triggering tsunamis on coasts near its epicenter. April 8  2008 earthquake 7.5 magnitude. The quake was in the southern Pacific Ocean, about 85 kilometers southwest ofVanuatu. May 12  2008 earthquake 8.0 magnitude about 60 kilometers northwest of Chengdu in the Sichuan province in China, killed over 65,000 people, expected to soar and China admits quake death toll could exceed 80,000.

Earthquakes in mythology and religion

In Norse mythology, earthquakes were explained as the violent struggling of the god Loki. When Loki, god of mischief and strife, murdered Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison would drip on Loki's face, forcing him to jerk his head away and thrash against his bonds, causing the earth to tremble.

In Greek mythology, Poseidon was the god of earthquakes.

Summary of Events and ActivitiesIt has been two years since the January 26, 2001, earthquake in India that left death and devastation in its wake. As one of the first humanitarian organizations to respond, CARE began providing lifesaving emergency supplies and services to four of the hardest-hit areas of Kutch District. Yet, even after basic needs were met -- and the television crews went home, CARE stayed on the scene to help survivors recover and rebuild. CARE partnered with The Federation of Indian Chambers of Commerce and Industry (FICCI) on the long-term recovery, including reconstruction of homes, schools, health clinics and community centers. CARE and FICCI

also supported people's ability to earn a living by providing training and support for agriculture and small businesses. Substantial progress has been made in the past 24 months. Now, as the construction of homes and community infrastructure nears completion, CARE work in close collaboration with communities, governments and local organizations to ensure these changes are effective and sustainable.The EarthquakeAs India commemorated its 51st Republic Day on Saturday January 26, a tremendous earthquake struck Gujarat State in the western part of the country. The quake's epicenter was near the town of Bhuj in Kutch District, but tremors from the quake, which registered 7.7 on the Richter scale, were felt deep into Pakistan and as far away as Nepal.

Estimates for the death toll ranged as high as 100,000 people, and buildings and infrastructure in many areas were completely destroyed.

After traveling to Bhuj's worst hit areas, CARE worker Renu Suri described the trauma of survivors immediately following the quake: "Life has come to a complete standstill. There are people roaming about on the roads, so stunned by events that they cannot participate in a discussion about what they need."

The words of Dawood Ismail, an earthquake survivor in Kutch, echo those of Dr. Suri. "There is nothing left

between the sky and the earth anymore. Everything has been demolished."

CARE's ResponseEarly the next morning following the quake, a team of nine disaster experts from CARE's main office in New Delhi was in Gujarat to assess the damage and coordinate relief priorities. Based on this assessment and in close coordination with government agencies, donors and other non-governmental organizations, CARE began an immediate relief effort in four of the most-affected areas of Kutch District: Anjar, Bhachau, Rapar and Bhuj.Emergency Phase: CARE distributed food and relief kits to about 10,000 families. Each relief kit contained:

One tarpaulin, two floor mats and three blankets to protect families from nighttime temperatures dipping below 40 degrees Fahrenheit.

One 10-liter jerrycan and 20 water purification tablets to ensure each family a clean water supply for up to three weeks; and

One lantern per family to provide light and security. CARE also assembled six medical teams, each consisting of a doctor and paramedic, that were rapidly mobilized to the field to provide medical assistance in the areas most in need. CARE also supplied first-aid equipment and basic medicines to anganwadi (community) centers in the four areas. By the end of February, CARE concluded the emergency phase of its relief activities, benefiting more than 10,000 families (50,000 people). Click here for a summary.

Longer Term Reconstruction Phase:The extent of damage in Gujarat and the depth of trauma experienced by its residents led CARE to commit to support for a longer-term reconstruction program. CARE partnered with the Federation of Indian Chambers of Commerce and Industry (FICCI) through the "FICCI-CARE Gujarat Rehabilitation Project. Together, the organizations implemented an 18- to 24-month reconstruction program in Bhachau, Anjar,

Rapar and Bhuj, four of the hardest-hit areas of Gujarat.As the project nears its completion, here are just some of the achievements:

FICCI and CARE have completed 4,982 earthquake resistant houses in 23 villages of Kutch, Gujarat. Each house is 30 square meters and has two rooms, a kitchen and an attached or community toilet. The remaining 18 homes will be completed by March 2003.

CARE and FICCI have rebuilt community buildings, such as schools, local government offices and health centers. So far, 15 schools, 10 community centers, 21 anganwadi(daycare) centers, 5 health centers and 12 panchayat ghars (local government offices) are complete. Three additional structures (a community center, a health center and an anganwadi center) are expected to be completed by March 2003.

The project is also helping villagers with basic services, such as access to clean drinking water, sanitation and new roads. To address the water shortage in Gujarat, the government is providing an access point at each village entrance; CARE and FICCI are supplying storage tanks and water pipelines. At the request of the villages, the project is also providing more hygienic sewage pipelines as well as village entrance gates to increase safety.

To help farmers begin replanting as soon as possible, CARE provided seeds and tools to 1,632 families. We also provided training in organic farming practices to 14 villages, demonstrated drip irrigation for 30 villages and distributed 1,200 irrigation kits.

To date, CARE has repaired 54 water-harvesting systems serving 10,500 farming families in 47 villages. In addition, the project expanded drinking water systems in six villages, reducing the distance women have to walk to collect water for their families. The project also revitalized damaged drinking water sources in the villages and supported the repair of 32 common wells serving 3,500 families in 30 villages.

The project has successfully introduced rooftop rainwater harvesting, in co-ordination with the ongoing reconstruction of homes. More than 90 rainwater-harvesting structures have been constructed in 30 villages. Approximately 5,000 litres of water can be harvested from each rooftop and stored in a cement tank. Three check dams have also been built.

To help villagers rebuild or strengthen their businesses, CARE established nine local business centers for making blocks. CARE provided resources and assistance to entrepreneurs who supplied construction blocks for the reconstruction.

CARE provided training to more 2,000 workers in masonry, plumbing, electrical repair, carpentry, welding and block making. These workers also learned about labor rights and laws. These trainees were organised into 10 village service guilds, which provide household services 8-10 villages each.

CARE trained 450 women, in food processing, handmade paper production, leather goods, bead work and other activities to improve their familys income.

With the destruction of primary healthcare infrastructure in the aftermath of the earthquake, CARE has been providing maternal and child health services through mobile clinics in remote rural villages. Currently, seven mobile clinics serve over 270,000 people, across 167 villages.

CARE in India:CARE began operations in India in 1950. Since 1982, CARE has been an active supporter of the Indian government's Integrated Child Development Services (ICDS) program, a nutrition and health program which serves millions of poor women and children, and is the largest program of its kind in the world. CARE helps

strengthen the capacity of ICDS anganwadi (rural health) centers to provide basic services that include the management of diarrhea and respiratory infections, immunizations, growth monitoring, health and nutrition education, and Vitamin A supplements. CARE also provides supplementary food rations to 6.6 million malnourished children, adolescent girls and pregnant and nursing women through ICDS. In India, CARE also manages numerous primary health care, small enterprise development and girls' education projects, and provides emergency relief to victims of natural disasters as needed. In 1999, CARE's relief and rehabilitation assistance in the wake of the deadly Orissa cyclones reached more than half a million people; six years earlier, CARE mounted a large relief program in the wake of an earthquake that killed some 9,000 people and injured 16,000 more in Maharashtra State. CARE's 500 experienced staff operate ongoing development programs in eight Indian states: Andhra Pradesh, Bihar, Madhya Pradesh, Maharashtra, Orissa, Rajasthan, Uttar Pradesh and West Bengal.

1. The definition of an earthquake is the release of sudden and extreme energy that is caused by shifting in the Earth's crust.

Facts About Earthquakesa. A seismometer is used to record and measure the strength of an earthquake.b. The Mercalli scale is used to measure the earthquake. Anything seven or above is considered

extremely dangerous.c. Earthquakes usually occur along fault lines, or cracks that occur within the Earth’s crust.d. Japan, New Zealand, Alaska are all located on one side of a horseshoe-shaped fault line called

the "Ring of Fire" that circles the Pacific Ocean and is responsible for frequent earthquakes and frequently erupting volcanos.

e. The "Ring of Fire" zone was responsible for the devastating earthquakes in Indonesia in 2004, in New Zealand in early 2011 as well as a 9.0+ quake and a series of offshore earthquakes in Japan in early 2011 which also resulted in a tsunami.

f. The San Andreas Fault is a fault line discovered in 1895 that stretches about one thousand and three hundred kilometers through California in the United States, and through Baja California in Mexico.

g. The San Andreas fault has been the cause behind a number of significant earthquakes, such as the San Francisco Earthquake in 1906, and the Loma Prieta Earthquake in 1989.

A shaking in San Francisco that measures 3.2 on the Richter scale is an example of an earthquake.

earthquake - Science Definition

A sudden movement of the Earth's lithosphere (its crust and upper mantle). Earthquakes are caused by the release

of built-up stress within rocks along geologic faults or by the movement of magma in volcanic areas. They are usually

followed by aftershocks. See Note at fault.

A Closer Look Fractures in Earth's crust, or lithosphere, where sections of rock have slipped past each other are

called faults. Earthquakes are caused by the sudden release of accumulated strain along these faults, releasing

energy in the form of low-frequency sound waves called seismic waves.Although thousands of earthquakes occur

each year, most are too weak to be detected except by seismographs,instruments that detect and record vibrations

and movements in the Earth. The point where the earthquake originates is the seismic focus, and directly above it on

Earth's surface is the earthquake's epicenter. Three kinds of waves accompany earthquakes. Primary (P) waves

have a push-pull type of vibration. Secondary (S) waves have a side-to-side type of vibration. Both P and S waves

travel deep into Earth, reflecting off the surfaces of its various layers. S waves cannot travel through the liquid outer

core. Surface (L) waves—named after the nineteenth-century British mathematician A.E.H. Love—travel along

Earth's surface, causing most of the damage of an earthquake. The total amount of energy released by an

earthquake is measured on the Richter scale. Each increase by 1 corresponds to a tenfold increase in strength.

Earthquakes above 7 on the Richter scale are considered severe. The famous earthquake that flattened San

Francisco in 1906 had a magnitude of 7.8.

earthquake

Primary and secondary waves radiate from an earthquake's focus and move through the Earth's interior. As they encounter a boundary, like that between the lower mantle and the liquid outer core, they are reflected and refracted. Secondary waves cannot travel through liquids. Surface waves radiate out from an earthquake's focus and travel only along the Earth's surface.

What Causes Earthquakes: Information about Faults, Plate Tectonics and Earth StructureQ: What is an earthquake and what causes them to happen?

Ans: An earthquake is caused by a sudden slip on a fault. Stresses in the earth's outer layer push the sides of the fault together. Stress builds up and the rocks slips suddenly, releasing energy in waves that travel through the earth's crust and cause the shaking that we feel during an earthquake. An EQ occurs when plates grind and scrape against each other. In California there are two plates the Pacific Plate and the North American Plate. The Pacific Plate consists of most of the Pacific Ocean floor and the California Coast line. The North American Plate comprises most the North American Continent and parts of the Atlantic Ocean floor. These primary boundary between these two plates is the San Andreas Fault. The San Andreas Fault is more than 650 miles long and extends to depths of at least 10 miles. Many other smaller faults like the Hayward (Northern California) and the San Jacinto (Southern California) branch from and join the San Andreas Fault Zone. The Pacific Plate grinds northwestward past the North American Plate at a rate of about two inches per year. Parts of the San Andreas Fault system adapt to this movement by constant "creep" resulting in many tiny shocks and a few moderate earth tremors. In other areas where creep is NOT constant, strain can build up for hundreds of years, producing great EQs when it finally releases.

Q: Can we cause earthquakes? Is there any way to prevent earthquakes?

Ans: Earthquakes induced by human activity have been documented in a few locations in the United States, Japan, and Canada. The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies. Most of these earthquakes were minor. The largest and most widely known resulted from fluid injection at the Rocky Mountain Arsenal near Denver, Colorado. In 1967, an earthquake of magnitude 5.5 followed a series of smaller earthquakes. Injection had been discontinued at the site in the previous year once the link between the fluid injection and the earlier series of earthquakes was established. (Nicholson, Craig and Wesson, R.L., 1990, Earthquake Hazard Associated with Deep Well Injection--A Report to the U.S. Environmental Protection Agency: U.S. Geological Survey Bulletin 1951, 74 p.) Other human activities, even nuclear detonations, have not been linked to earthquake activity. Energy from nuclear blasts dissipates quickly along the Earth's surface. Earthquakes are part of a global tectonic process that generally occurs well beyond the influence or control of humans. The focus (point of origin) of earthquakes is typically tens to hundreds of miles underground. The scale and force necessary to produce earthquakes are well beyond our daily lives. We cannot prevent earthquakes; however, we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety.

Q: What do we know about the interior of the Earth?

Ans: 

Five billion years ago the Earth was formed by a massive conglomeration of space materials. The heat energy released by this event melted the entire planet, and it is still cooling off today. Denser materials like iron (Fe) sank into the core of the Earth, while lighter silicates (Si), other oxygen (O) compounds, and water rose near the surface. The earth is divided into four main layers: the inner core, outer core, mantle, and crust. The core is composed mostly of iron (Fe) and is so hot that the outer core is molten, with about 10% sulfur (S). The inner core is under such extreme pressure that it remains solid. Most of the Earth's mass is in the mantle, which is composed of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O) silicate compounds. At over 1000 degrees C, the mantle is solid but can deform slowly in a plastic manner. The crust is much thinner than any of the other layers, and is composed of the least dense calcium (Ca) and sodium (Na) aluminum-silicate minerals. Being relatively cold, the crust is rocky and brittle, so it can fracture in earthquakes. (Univ. of Nevada).

Q: What are plate tectonics?

Ans: Plate tectonics is the continual slow movement of the tectonic plates, the outermost part of the earth. This motion is what causes earthquakes and volcanoes and has created most of the spectacular scenery around the world.

Q: What is a fault and what are the different types?

Ans: A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. This movement may occur rapidly, in the form of an earthquake - or may occur slowly, in the form of creep. Faults may range in length from a few millimeters to thousands of kilometers. Most faults produce repeated displacements over geologic time. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other. The fault surface can be horizontal or vertical or some arbitrary angle in between.

 Earth scientists use the angle of the fault with respect to the surface (known as the dip) and the direction of slip along the fault to classify faults. Faults which move along the direction of the dip plane are dip-slip faults and described as either normal or reverse, depending on their motion. Faults that move horizontally are known as strike-slip faults and are classified as either right-lateral or left-lateral. Faults, which show both dip-slip and strike-slip motion are known as oblique-slip faults.

The following definitions are adapted from The Earth by Press and Siever.

Normal fault- a dip-slip fault in which the block above the fault has moved downward relative to the block below. This type of faulting occurs in response to extension and is often observed in the Western United States Basin and Range Province and along oceanic ridge systems.

Thrust fault- a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. This type of faulting is common in areas of compression, such as regions where one plate is being sub ducted under another as in Japan. When the dip angle is shallow, a reverse fault is often described as a thrust fault.

Strike-slip fault - a fault on which the two blocks slide past one another. The San Andreas Fault is an example of a right lateral fault.

A left-lateral strike-slip fault is one on which the displacement of the far block is to the left when viewed from either side.

A right-lateral strike-slip fault is one on which the displacement of the far block is to the right when viewed from either side.

Q: At what depth do earthquakes occur?

Ans: Earthquakes occur in the crust or upper mantle, which ranges from the earth's surface to about 800 kilometers deep (about 500 miles).

Q: What is "surface rupture" in an earthquake?

Ans: Surface rupture occurs when movement on a fault deep within the earth breaks through to the surface. NOT ALL earthquakes result in surface rupture.

Q: What is the relationship between faults and earthquakes? What happens to a fault when an earthquake occurs?

Ans: Earthquakes occur on faults - strike-slip earthquakes occur on strike-slip faults, normal earthquakes occur on normal faults, and thrust earthquakes occur on thrust or reverse faults. When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other. The fault surface can be vertical, horizontal, or at some angle to the surface of the earth. The slip direction can also be at any angle.

Q: How do we know a fault exists?

Ans:

1. if the EQ left surface evidence, such as surface ruptures or fault scarps (cliffs made by EQs).2. if a large EQ has broken the fault since we began instrumental recordings in 1932.3. if the faults produces small EQs that we can record with the denser seismographic network established in the 1970s.

Q: Where can I go to see the/a fault?

Ans: The closest fault depends on where you live. Some earthquakes produce spectacular fault scarps, and others are completely buried beneath the surface. Sometimes you may not even know that you are looking at a fault scarp.

Q: What does an earthquake feel like?

Ans: Generally, during an earthquake you first will feel a swaying or small jerking motion, then a slight pause, followed by a more intense rolling or jerking motion. The duration of the shaking you feel depends on the earthquake's magnitude, your distance from the epicenter, and the geology of the ground under your feet. Shaking at a site with soft sediments, for example, can last 3 times as long as shaking at a stable bedrock site such as one composed of granite. If the site is in a building, then the height of the building and type of material it is constructed from are also factors. For minor earthquakes, ground shaking usually lasts only a few seconds. Strong shaking from a major earthquake usually lasts less than one minute. For example, shaking in the 1989 magnitude 7.1 Loma Prieta (San Francisco) earthquake lasted 15 seconds; for the 1906 magnitude 8.3 San Francisco earthquake it lasted about 40 seconds. Shaking for the 1964 magnitude 9.2 Alaska earthquakes, however, lasted three minutes.

Q: Foreshocks, aftershocks - what is the difference?

Ans: "Foreshock" and "aftershock" are relative terms. Foreshocks are earthquakes, which precede larger earthquakes in the same location. Aftershocks are smaller earthquakes, which occur in the same general area during the days to years following a larger event or "mainshock", defined as within 1-2 fault lengths away and during the period of time before the background seismicity level has resumed. As a general rule, aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the main shock. The frequency of these aftershocks decreases with time. Historically, deep earthquakes (>30km) are much less likely to be followed by aftershocks than shallow earthquakes. (Univ. of Washington).

Q: Two earthquakes occurred on the same day. Are they related?

Ans: Often, people wonder if an earthquake in Alaska may have triggered an earthquake in California; or if an earthquake in Chile is related to an earthquake that occurred a week later in Mexico. Over these distances, the answer is no. Even the Earth's rocky crust is not rigid enough to transfer stress fields efficiently over thousands of miles.

Objectives

Upon successful completion of this unit students will be able to:

describe the effects of earthquakes in terms of human and economic losses and illustrate with few examples;

explain the characteristics of earthquakes and identify typical earthquake representations (records) used for earthquake engineering studies and design;

explain the four main types of damaging effects of earthquakes, and explain two important terms related to building reaction to earthquakes i.e. 

inertial forces and the fundamental period of vibration.

Background

Earthquakes are natural disasters of a generally unpredictable nature. In spite of considerable efforts made towards improving the understanding of these natural disasters and protecting built environment from their effects, earthquakes still cause huge human and economic losses; this is true both for highly industrialized and lesser developed countries. Recent examples of earthquakes which caused significant economic losses are the 1994 Northridge (California) earthquake which killed 57 people and caused the economic loss of approximately $40 billion, and the 1995 Great Hanshin (Kobe, Japan) earthquake that killed more than 5,000 people and caused the economic loss of $110 billion. Some other recent earthquakes caused smaller economic losses, however these events caused a significantly larger number of fatalities, e.g. the recent 1999 Izmit (Turkey) earthquake caused 15,000 deaths and the 1993 Killari (India) earthquake caused 10,000 deaths. Also, September 1999 Chi-Chi (Taiwan) earthquake caused over 2,400 deaths and the economic loss of over $30 billions. Most of the human and economic losses in these earthquakes were due to the collapse of buildings and other man-made structures.

Collapse of a residential building in the 1995 Kobe (Japan) earthquake (magnitude 7 on the Richter scale)

A general study of earthquakes includes: consideration of the nature of ground faults, the propagation of shock waves through the earth mass, the specific nature of recorded major quakes, etc. However, the material presented here is focused mainly on the basic concepts of designing the buildings capable to resist earthquake effects, which is a scope of earthquake engineering, the branch of engineering devoted to mitigating

earthquake hazards.

Earthquake engineering covers the investigation and solution of the problems created by damaging earthquakes, and consequently the work involved in the practical application of these solutions, i.e. in planning, designing, constructing and managing earthquake-resistant structures and facilities.

In the following section we are going to describe the characteristics of earthquakes of relevance to earthquake engineering studies.

Characteristics of Earthquakes

A major earthquake   is usually rather short in duration, often lasting only a few seconds and seldom more than a minute or so.

In general, during a quake there are usually one or more major peaks of magnitude of motion. These peaks represent the maximum effect of the quake.

Although the intensity of the quake is measured in terms of the energy release at the location of the ground fault, the critical effect on the given structure is determined by the ground movements at the location of the structure. The effect of these movements is affected mostly by the distance of the structure from the epicenter, but they are also influenced by the geological conditions directly beneath the structure and by the nature of the entire earth mass between the epicenter and the structure.

Modern recording equipment and practices provide us with representations of the ground movements at various locations, thus allowing us to simulate theeffects of major earthquakes. One of the most common earthquake representations is acceleration of the ground in one horizontal direction plotted as a function of elapsed time; a typical acceleration record of an earthquake is shown on the figure below. For use in physical tests in laboratories or in computer modeling, records of actual quakes may be "played back" on structures in order to analyze their responses.

Acceleration vs. time record of the 1940 Imperial Valley, California earthquake at the El Centro Station (this is one of the most popular earthquake records)

Although it may seem like a gruesome way to achieve it, we advance our level of competency in design every time there is a severe earthquake that results in some major structural damage to buildings. Engineering societies (e.g. Earthquake Engineering Research Institute of Oakland, California) and other groups routinely send investigating teams to the sites of major quakes to report on the effects on buildings in the area. Of particular interest are the effects on recently built structures, because these buildings are, in effect, full-scale tests of the validity of our most recent design techniques. Each new edition of the building codes reflects some of the results of this cumulative growth of knowledge gained from the latest disasters.

This section has been developed based on the by Ambrose's and Vergun's book (see Resources section for the complete reference).

General Effects of Earthquakes

The ground movements caused by earthquakes can have several types of damaging effects. Some of the major effects are:

Ground shaking, i.e. back-and-forth motion of the ground, caused by the passing waves of vibration through the ground;

Soil failures, such as liquefaction and landslides, caused by shaking; Surface fault ruptures, such as cracks, vertical shifts, general settlement of an 

area, landslides, etc. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that 

can cause major damage to shoreline areas.

A dramatic illustration of several building collapses (entire buildings tilted over) induced by soil failure (liquefaction) in the 1964 Niigata (Japan) earthquake is shown in the figure below.

Additional damage can be caused by fires or gas explosions started by the shaking or by flooding from failures of dams, etc.

Although all these possible effects are of concern, structural engineers are directly concerned about the effects of ground shaking to building structures.

A comparative study on the Earthquake Information Management Systems (EIMS) in India, Afghanistan and IranSima Ajami

Additional article information

Abstract

Context:

Damages and loss of life sustained during an earthquake results from falling structures and flying glass and objects. To address these and other problems, new information technology and systems as a means can improve crisis management and crisis response. The most important factor for managing the crisis depends on our readiness before disasters by useful data.

Aims:

This study aimed to determine the Earthquake Information Management System (EIMS) in India, Afghanistan and Iran, and describe how we can reduce destruction by EIMS in crisis management.

Materials and Methods:

This study was an analytical comparison in which data were collected by questionnaire, observation and checklist. The population was EIMS in selected countries. Sources of information were staff in related organizations, scientific documentations and Internet. For data analysis, Criteria Rating Technique, Delphi Technique and descriptive methods were used.

Results:

Findings showed that EIMS in India (Disaster Information Management System), Afghanistan (Management Information for Natural Disasters) and Iran are decentralized. The Indian state has organized an expert group to inspect issues about disaster decreasing strategy. In Iran, there was no useful and efficient EIMS to evaluate earthquake information.

Conclusions:

According to outcomes, it is clear that an information system can only influence decisions if it is relevant, reliable and available for the decision-makers in a timely fashion. Therefore, it is necessary to reform and design a model. The model contains responsible organizations and their functions.

Keywords: Crisis management, destruction, earthquake, information systems, natural disaster

INTRODUCTION

Iran, because of extent, geographical situation and climatic variety, is one of the damageable countries of the world.[1] Natural disasters, for example earthquake, are an unexpected event that cause damage and destruction to human life and health, and the injured persons without others assistance are not able to meet their need. Earthquakes in Iran and neighboring regions (e.g., India, Turkey and Afghanistan) are closely connected to their position within the geologically active Alpine-Himalayan belt[2–5] [Table 1]. This crisis happens in an especial situation that changes all of the daily affairs of disastrous society, such as people earning, city services, communication system and community public needs and people health.[6] Earthquake Information Management System (EIMS) is a system that records, collects, keeps, retrieves and analyzes inputs and alters the reports and required earthquake information (EI) and renders it to the right people and organization to manage earthquake outcomes.[7]

Table 1

Deadliest earthquakes by year, 1995–2005

Information is not an end in itself, but a means to better decisions in policy design, planning, management, monitoring and evaluation of programs and services, including damage of disasters reduction.[8] Unfortunately, information systems in most countries are inadequate in providing the needed management support. Earthquake loss estimates are forecasts of damage and human and economics impacts that may result from future earthquakes. These estimates are based on current scientific and engineering knowledge.[9] The “earthquake loss estimation methodology” is a system that uses mathematical formulas and information about building stock, local geology and the location and size of potential earthquakes, economic data and other information to estimate losses from a potential earthquake. EIMS uses Arc GIS (Geographical Information System) to map and display ground shaking, the pattern of building damage and demographic information about a community. Once the location and size of a hypothetical earthquake is identified, EIMS will estimate the violence of the following: ground shaking, the number of buildings damaged, the number of injured persons, the amount of damage to transportation systems, disruption to the electrical and water utilities, the number of people displaced from their homes and estimated cost of repairing projected damage and other effects.[10–13] An estimate of losses from future earthquakes is essential to preparing for a disaster and facilitating good decision making at the local, regional, province and national levels of government. An EIMS can estimate earthquake losses, providing vital tools for the following:

1)

Land-use planning and facility site decisions (e.g., a map-based analysis of the potential intensity of ground shaking from a postulated earthquake that identifies those parts of the community that will experience the most violent shaking and the buildings at greatest risk of damage).

2)

Prioritization of retrofit or abatement programs (e.g., an estimate of building damage that provides the basis for establishing programs to mitigate or strengthen buildings that may collapse in earthquakes by providing estimates of damages and casualties).

3)

Regional, province and local emergency response and contingency planning (e.g., estimates of casualties and of damage to buildings and utilities).

4)

Medical and relief agency preparedness and response (e.g., estimates of casualties and homelessness).

5)

Assistance planning.[11]

In this research, our important questions were:

1. When can EIMS be useful?2. What are the essential substructures in EIMS?3. What is the usage of EIMS?4. What are the stages for formulating EIMS?5. How do we use EIMS to prepare for earthquakes?

In this study, the management network for information related to earthquake in India and Afghanistan was compared with Iran to determine the total score of EIMS in them. Then, weaknesses and strengths points were determined. At last, several recommendations and a model were proposed to decrease weaknesses, improve the efficiency of EIMS process and, therefore, reduce damages and loss and expedite relief to victims after earthquakes.

MATERIALS AND METHODS

This research was practical and the study was an analytical comparison. The statistical population consisted of the EIMS on network in India, Afghanistan and Iran. Countries such as Iran, India and Afghanistan were chosen because these countries have high rate of disasters, especially earthquakes.

To perform this study, the researcher made forms and questionnaires. The method of collecting information was interview and observation. The forms contained items to define standard characteristics of the Information Management System that was extracted from JCAHO; Joint Commission on Accreditation of Healthcare Organization, AHIMA; American Health Information Management Association and CCHSA; Canadian Council on Health Services Accreditation,[14] and then made synthetic forms. The questionnaire was designed to determine viewpoints and opinions of experts to set weights for every characteristic of the EIMS. In the first phase of data collection, validity of forms and questionnaire was approved too. The source of information contained Internet, personnel, documentations, journals and books. Data included EI sources, method of recording, storing, retrieving, analyzing, interpreting, distributing of EI, national and international levels usage, and so on.

Data were gathered from the Internet, personnel, journals and books. Criteria Rating Technique[15] and descriptive method were used to analyze findings.

Standard characteristics of the Information Management System were selected as criteria. In the second stage, for comparing characteristics of EIMS, experts’ opinions were selected to set weights (the relative importance of each criterion from 1 was low until 10 was high) by brainstorm decision criteria and measured mean of experts’ opinions to set weights for each of them in Table 1. Rating was established (ratio = weight of each criteria divided by sum). Then, scales (positive = 4, moderate = 3, not access = 2, negative = 1) and scores (score = ratio*scale) for selected countries were calculated.

RESULTS

Findings showed follow answers for our questions.

When can EIMS be useful?

1)

Information users and addressers specified,

2)

Time, form and mechanism of information distributed specified,

3)

EI must be valid and reliable,

4)

Fast access to EI.

Furthermore, the data received are often not helpful for management decision making because they are incomplete, inaccurate, untimely and unrelated to priority tasks and functions of crisis management.

Essential sub-structures in EIMS:

1)

Science of Crisis Management,

2)

Information Technology,

3)

Geographic Information System,

4)

Information System,

5)

Mass media,

6)

Cell phone,

7)

Capital,

8)

Human resources.

Usage of EIMS:

1)

Impossibility of fast and easy retrieval, extract and access of information for managers and all related users;

2)

Extract integrated data from different resources;

3)

Prevent to implement parallel and repeated activities by various organizations;

4)

Decrease cost and time;

5)

Assessing and monitoring function and plans before and after earthquakes;

6)

Recognizing training needs functional forces;

7)

Formulate prevention, action and rehabilitation according to outcomes of EIMS evaluating.

Formulating EIMS's stages:

1)

Institute joint commission from related governmental and non-governmental sectors and organizations;

2)

Determine elementary sources;

3)

Determine and formulate general concepts and purposes;

4)

Recognize necessary data items;

5)

Recognize and determine informatics resources;

6)

Recognize and determine registration, collection and storage methods and administrators;

7)

Recognize and determine retrieval and analyze methods and administrators;

8)

Recognize and determine, distribute and issue of information methods and administrators;

9)

Create methods to connect systematically among these administrators;

10)

Notice to render feedback process in EIMS to ensure continuous improvement system;

11)

Dynamic and flexible plans and functions must be design.

How do we use EIMS to prepare for earthquakes?

The first step in preparing for a disaster is estimating its potential impact. Loss estimates can provide the basis for developing mitigation policy, for developing and testing emergency preparedness and response plans and for planning for post-disaster relief and recovery.[16]

• Before an earthquake:

A reducing earthquake loss begins before the earthquake. Loss estimates provide public and private sector agencies with a basis for planning, zoning, building codes and development regulations, and

policy that would reduce the risk posed by violent ground shaking and ground failure. Loss estimates can also be used to evaluate the cost-effectiveness of alternative approaches to strengthening potentially hazardous structures.

• Before an earthquake:

Preparing to respond, understanding the scope and complexity of earthquake damage is essential to effective preparedness. EIMS can forecast damage to buildings, casualties and disruption of utilities. These estimates can serve as the basis for developing emergency response plans and for organizing tests and exercises of response capability.

About EIMS: In India, findings showed that the Disaster Information Management System (DIMS) was launched by SRISTI “SRISTI”;http://www.sristi.org Society for Research and Initiatives for Sustainable Technologies and Institutions on the 18th of January 2002 at the Indian Institute of Management, Ahmedabad, Gujarat, India. SRISTI participated in the relief and rehabilitation work in Kutch. However, the relief work suffered immensely due to lack of information and proper planning. When we tried to get answers to important questions that were cropping up – for instance, whether there is a database on the distribution of available resources and expertise with individuals, institutions and corporations – all we got in response was a blank. This pointed to the urgent necessity of building a system for disaster mitigation and for documenting experiences of individuals and organizations, which might act as a knowledge resource and help in better coordination in case of future disasters. Thus, SRISTI initiated an effort to build a “Disaster Management Information System.” Through this initiative, we are trying to develop a database-driven information system for Disaster Management Authorities (DMA) in various states, NGOs and other organizations. We appealed to NGOs, relief workers, DMAs and individuals to share their experiences and volunteer services and resources to the online database maintained at our website. The database currently contains more than a thousand volunteers who have offered to volunteer their services and resources in time of emergency. About 700 organizations and institutions indexed on the site, besides other resources and web links. The DMIS is a voluntary activity run with contributions in terms of time and services by SRISTI volunteers, NGOs and, above all, civil society institutions across the world. All the information shared with us is accessible to all, except where the volunteer has chosen to limit accessibility only to the relevant authorities.[17]

About EIMS: In Afghanistan, findings showed that Afghanistan is in danger of many natural disasters. Therefore, it needs to have a DIMS, especially EIMS. Disaster management is a legal attempt that needs miscellaneous information, different locations and tenses, and this information must have a true format to be in access of key staff in deciding. The temporary project of “Management Information for Natural Disasters” in Kabul province and Kunduz province in Afghanistan has been doing well for 8 months. Aims of this temporary project were expanding a crisis information management system. Also, it updates and gives information to governments. This project has increased Afghanistan's ability in crisis management nationally, supporting educated people and city renewing services by building governmental organizations in management information for natural

disasters. Natural disaster management in these two provinces is mostly based on estimating the amount of damages and concentrated rescue operations, and there is no system to avoid or decrease the amount of damages by natural disasters. Before or after disaster, management is very weak in these countries and they are dependent on UN or NGO. Information source in the process of collecting EIMS includes human forces and geographical informative systems that are a dangerous area and shows locations with high potential danger. In this system, the satellite has an important part in recognizing crisis locations distance.[18] To record collected information, a team of Information System Unit is educated to record in puts portions, information and management of stations of informative system of disaster management, and they will record the information. Structure of DIMS special earthquake is not useful in many parts of the country. The most important problem is lack of exact information (not in time).

In Iran, the EIMS showed absence of timely reporting of most of the data before, during and after earthquakes, Defective, insufficient and inaccurate registration of data, declaration and publishing different and contradictory population statistical reports by related organizations and weakness to use reliable information to support the prevention systemic planning. In order to make suitable EI in Iran, we need to provide and support managers. To improve current situation of EIMS, we need to design a midified model of EIMS.[1] The modified model contains; responsible organizations, their functions, and flow-work that were approved by the Delphi Technique.

Table 2 denotes the highest sum of score relative to India and the lowest relative to Iran. The weakness issues are respectively concluded: EI stores systematically, no parallel and repeated activities by various organizations and accessibility of EI easy and fast in EIMS’ criteria in Iran. In the range of ranks, Afghanistan and India were classified in the very good range and Iran in the moderate range.

Table 2

EIMS characteristics evaluating in selected countries

DISCUSSION

Mass media is imperative in communicating news and information to the public. Responsible journalism can also help clear inaccurate rumors and influence public's attitude toward preparing for disasters. Moreover, press coverage of old disasters may be a good source of data where official records do not exist. However, the present study has revealed that the press has largely failed in

terms of disaster mitigation and preparedness guidance. It seems that media is more interested in giving disastrous news than informing the public. Turkish media had been more influential in urging both the public and the officials in getting ready for the coming earthquakes. Television appears to be a better tool for this purpose.[19]

The Japan Meteorological Agency (JMA) as a governmental organization responsible for issuing EI and tsunami forecasts had developed an early earthquake notification system in Japan. At present, JMA issues the following kinds of information successively when a large earthquake occurs: (1) prompt report of occurrence of a large earthquake and major seismic intensities caused by the earthquake in about 2 min after the earthquake occurrence, (2) tsunami forecast in around 3 min, (3) information on expected arrival times and maximum heights of tsunami waves in around 5 min and (4) information on a hypocenter and a magnitude of the earthquake, the seismic intensity at each observation station, the times of high tides in addition to the expected tsunami arrival times in 5–7 minutes. To issue the above information, JMA has established an advanced nationwide seismic network with about 180 stations for seismic wave observation and about 3400 stations for instrumental seismic intensity observation, including about 2800 seismic intensity stations maintained by local governments.[20]

Beginning in the late 1950s in the world, planners started to develop and use computerized models, planning information systems and decision-support systems to improve performance. They have found tools to enhance their analytical, geospatial technologies that differ from one country to another. The industrialized information societies are well adapted to this technology. They use it in many fields; the governments apply urban information systems in all aspects of the planning process, including data collection, storage, data analysis and presentation, planning and policymaking, communication with the public, policy implementation and administration. The United States is the pioneer in this field; they began working with urban information systems in the 1970s. Canada and Australia have developed systems; also European countries like France, Germany and Holland have been successful in applying these technologies. Turkey is a latecomer in this field because of financial problems, the other priorities and the lack of technical expertise and different mentalities of the administrators. But today, urban information system is a popular magic word in the local governments. The first initiative of local governments like Bursa and Ayden cities began to use urban information systems in the mid-1990s, and then the other three metropolitan municipalities, Istanbul, Ankara and Izmir, made studies about digitizing the maps, plans and creating inventories about their cities. In this section, first, Turkey examples and their studies about urban information systems are explained, then the other world examples are described for their different uses and applications. In

the earthquake management section, there is a disaster management cycle showing the actions and preparedness. The phases are based in this cycle. The preparedness and mitigation phases have more emphasis. Because it is believed that besides advice and instructions given to the public, raising awareness for the earthquake risk is necessary for the management levels and the residents, the technological tools help in this process. But, the management, including protection and recovery, is completed with the interrelated system.[21]

CONCLUSION

The first effort to systematically collect and analyze data in developing countries should be undertaken by national program managers. Based on the investigation of the current situation in India, Afghanistan and Iran, we need to have EIMS because of the following reasons:

1)

Relevance of the information must be gathered;

2)

Continuous improvement of data must be concerned;

3)

Control and manage natural disasters (rapid availability and retrieval EI);

4)

Timely reporting and feedback must be rendered;

5)

Analyze information and render reports and define strengths, weaknesses, threats and opportunities;

6)

Monitoring healthcare services status and services needs;

7)

Coordinating activities between government and non-government sectors and other related sectors to use EI;

8)

Determining causes of deaths and health priorities and planning to decrease mortality after earthquake in the future;

9)

Using outcomes for determining cause of earthquake mortalities and other related problems to prevention in the future;

10)

Formulating strategies to diseases incidence prevention and decrease of controllable deaths after earthquakes on wards.

After an earthquake, a rapid response to a damaging earthquake will reduce loss of life, lessen complications from injuries and secondary damage and loss and expedite relief to victims.

Reliable and up-to-date information can have an impact on the destruction factors and prevent them. Because of the financial and human damages of disasters, establishing a general, scientific and practical management network is necessary.

Figure 1 demonstrates a proposed model that shows the process of relationships between organizations related to EIMS in Iran. In this model, duty and function of every organization is determined. These duties are classified according to registering and collecting earthquake data, storing and processing, analyzing and distributing and using issued EI.

Figure 1

The proposed model that shows process of relationships between organizations related to EIMS in Iran

ACKNOWLEDGMENT

The author would like to thank Misses Z. Moradi, Mahshid Fattahi and N. Nematolahi for helping to fulfill this research.

Footnotes

Source of Support: Nil

Conflict of Interest: None declared

Article informationJ Educ Health Promot. 2012; 1: 27.

Published online Aug 22, 2012. doi: 10.4103/2277-9531.99963

PMCID: PMC3577382

Sima Ajami

Department of Health Information Technology, Health Management and Economics Research Center, Isfahan University of Medical Sciences, Isfahan, Iran

Address for correspondence: Sima Ajami, Associate Professor, Department of Health Information Technology, Health Management and Economics Research Centre, School of Medical Management and Information Sciences, Isfahan University of Medical Sciences, Isfahan, P.O.Box: 81745-346, Iran. E-mail: Ajami/at/mng.mui.ac.ir

Copyright : © 2012 Ajami S.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Articles from Journal of Education and Health Promotion are provided here courtesy of Medknow Publications

REFERENCES1. Tehran, Iran: [Last cited in 2005]. Institute of Management and Planning Studies, Tehran, Iran. The role of community knowledge in disaster management: The bam Earthquake lesson in Iran. Available from:http://www.engagingcommunities2005.org/abstracts/593-bamdad-n.html .

2. Tavakoli N. Health information management in disaster’ proceeding of second national health and management disaster meeting. Tehran, Iran: 2004. Nov 24–26,

3. Rastegari H, Ajami S. An overview of the management of a crisis. Health Inf Manag. 2005;2:73.

4. Ajami S. The role of information management in rendering healthcare in disasters. In Proceeding of Second National Health and Management Disaster meeting, Tehran, Iran. 2004 Nov 24–26;

5. The U.S. Geological Survey, Earthquake Hazards Program. Disaster Management Information System, fact sheet 04: Largest and Deadliest Earthquakes by Year 1990 – 2005’. [Last cited in 2009]. Available from: http://www.sristi.org/dmis/facts .

6. Division of International Health, Department of Health and Human Services, Centers for Disease Control and Prevention, Epidemiology Program Office. Public Health Systems Development; Health Information Systems. [Last cited in 2000]. [online]. United States. Available from: http://www.cdc.gov/epo/dih/systems.html .

7. Seismological Bureau of Yunnan Province. Improvement of Earthquake disaster reduction and early warning systems. [Last cited in 2001]. [online]. PR, China. Available from: http://www.chinaproject.network .

8. Lippeveld T, Sauerborn R, Bodart C. Design and implementation of health information systems. Geneva, Switzerland: World Health Organization; 2000.

9. Rock ML. Effective crisis management planning: Creating a collaborative framework [online] Educ Treat Child J. 2000;23:248–64.

10. Seeger MW, Sellnow TL, Ulmer RR. Communication and organizational crisis.USA: Praeger; [Last modified 2006 Apr 11]

11. Kabirzadeh A. In Proceeding of Natural Health and Management of Disaster Meeting. Tehran, Iran: 2003. May 27-29, Disease control and prevention after natural disaster.

12. Ajami S, Fatahi M, Moradi Z, Nematolahi N. Proceeding of International Disaster Reduction Conference (IDRC) Switzerland, Davos: From 27 August to first of September 2006; An analysis studies on Earthquake Information Management Systems (EIMS) in Japan, Afghanistan and Iran and proposing a suitable model for Iran.

13. Ajami S, Fatahi M, Moradi Z. Proceeding of International Disaster and Risk Conference IDRC. Switzerland, Davos: Reduce destroys and rule of Earthquake Information Systems the Comparative study in Turkey, Afghanistan and Iran. from August 25 to August 29, 2008.

14. Ajami S, Tavakolimoghadam O. The study of information management system of medical records office in Kashani hospital based on the existing standards. Health Inf Manage J. 2006;3:63–9.

15. Chang R. Success through Teamwork: A Practical Guide to Interpersonal Team Dynamics (High-Performance Team Series) (Paperback) Homa-ye-Salamat.2006;2:63–5. [in Persian]

16. Ajami S, Fatahi M. The role of earthquake information management systems (EIMSs) in reducing destruction: A comparative study of Japan, Turkey and Iran.Disaster Prev Manag. 2009;18:150–61.

17. Society for Research & Initiatives for Sustainable Technologies and Institutions Organization. Disaster Management Information System’ [online] [Last cited in 2009]. Available from: http://www.sristi.org/dmis/dmi_system .

18. Information Management for Natural Disasters: Pilot Project for Kabul & Kunduz Province. 2005, Kabul and Kunduz Province. Afghanistan: [Last cited in 2005]. Afghanistan Information Management Service (AIMS) Project [United Nations Development Program (UNDP)] Available from: http:// www.aims.org.af/services/sectoral/d_m/dmis_for_afg_a_p_p.pdf .

19. Dedeoglu N. Proceeding of International Disaster Reduction Conference (IDRC)Switzerland, Davos: 2008. Role of the Turkish news media in disaster preparedness. From August 25 to August 29, 2008.

20. Doi K, Kato T. Real time Earthquake information system in Japan. American Geophysical Union, Fall Meeting. 2003 Abstract # S21B-03-12/2003.

21. Yaliner O. Description of Urban information system and emergency management concepts, examples in Turkey and in the World. In Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Geodetic and Geographic Information Technologies a Thesis Submitted to the Graduate School of Natural and Applied Sciences of the Middle East Technical University. 2002 Jan

What causes Earthquakes?

Global Map of Plate Tectonics

Plate TectonicsEarth's outer layer is broken into pieces called tectonic plates which are about 100km thick and are constantly moving towards, away from or past each other. For example, the plate containing Australia and India is moving north at the rate of 7cm a year, causing an intracontinental collision with the Eurasian Plate in the Himalayas. That is why these mountains are so high. Because continents are part of these plates, they also move. An earthquake occurs when the rocks break and move as a result of stresses caused by plate movements.

Most earthquakes occur on the boundaries between plates, where one plate is forced under another such as happens off island chains such as Japan, Indonesia or the Solomon Islands, or past another as occurs in California and New Zealand. Some regions have more earthquakes than others with 80 per cent of all recorded earthquakes taking place around the edge of the Pacific Plate, including New Zealand, Papua New Guinea, the Solomon Islands, Vanuatu, Japan, Canada, USA and South America.

In areas where plates collide, earthquakes can occur down to depths of 700km. In areas where plates slide past each other, such as California or New Zealand, earthquakes are shallower. Shallow earthquakes also occur where plates are pulling away from each other along under sea ridges, and the oceans are growing bigger, like the plate margin between Australia and Antarctica.

Intraplate EarthquakesEarthquakes that do not occur on plate margins are called intraplate earthquakes. All earthquakes on mainland Australia and Tasmania are intraplate. On studying these intraplate earthquakes in various continents, seismologists have found that most of them are caused by thrust faulting due to the rocks being squeezed or compressed. It seems that the movement of the tectonic plates causes the rocks away from their margins to be compressed. Intraplate earthquakes are not as common as those on plate margins, but major earthquakes with magnitudes of 7.0 or more do happen occasionally.

Volcanic EarthquakesMolten rock, called magma, is stored in reservoirs under volcanoes. As this magma moves upwards, it can fracture the rock it squeezes through, causing earthquakes, usually with magnitudes not much greater than 5.0. Sometimes the magma collects in a high level reservoir prior to a volcanic eruption and as it moves around it causes bursts of continuous vibration, called volcanic tremor. Because of these precursors, seismographs (earthquake recorders) are very useful for monitoring volcanoes to give warning of an impending eruption.

Foreshocks and AftershocksForeshocks are smaller earthquakes that may occur in the same area as a larger earthquake that follows. They are caused by minor fracturing of rocks under stress prior to the main break that happens during the largest earthquake of the series, called the mainshock. Foreshocks can start up to a year before the mainshock, as was the case before the three large (magnitudes between 6.3 and 6.7) earthquakes near Tennant Creek in January 1988. Not all earthquakes have foreshocks, and sometimes a series of similar sized earthquakes, called an earthquake swarm, happens over months without being followed by a significantly larger mainshock. This limits the usefulness, at this stage, of foreshocks in earthquake prediction.

Aftershocks are smaller earthquakes that may occur after the mainshock, in the same area. They are caused by the mainshock area readjusting to the fault movement, and some may be the result of continuing movement along the same fault. The largest aftershocks are usually at least half a magnitude unit smaller than the mainshock and the aftershock sequence may continue for months or years after the mainshock. Not all earthquakes have aftershocks – the magnitude 5.6 Newcastle earthquake in 1989 only had one aftershock, which was very small with a magnitude of 2.1. Occasionally, small earthquakes with magnitudes between 3.0 and 3.5 have aftershocks. This has been observed in the Dalton-Gunning area, north of Canberra.

Effects of Earthquake

The effects of an earthquake include fire, loss of lifes, tidal waves that cause tsunami, avalanches, flooding, broken gas lines and destroy of roads and bridges. Other effects include building damages and spilling of hazardous chemicals.

The effect of an earth quake is dependent on its strength and magnitude. An earth quake strong in both strength and magnitude leads to the destruction of property, landslides and tsunamis if the area

is close to a water body. Mild earth quakes cause minimal damage like cracks on building walls and swaying of buildings.

 The effects of earthquakes include: avalanches, tidal waves (tsunamis), fires, flooding, death, building damage, destruction of infrastructures, broken gas lines and spills of hazardous chemicals. An earthquake is the consequence of an abrupt release of energy in the Earth's crust that generates seismic waves.

 The effects of earthquakes include: direct shaking of manmade structures such as buildings and bridges, landslides and liquefaction due to the stress of seismic waves and tsunamis off the coasts of affected regions. Tsunamis typically have waves that reach up to 10 meters.

 The effects of earthquakes include damage to buildings and in worst cases the loss of human life. The effects of the rumbling produced by earthquakes usually leads to the destruction of structures such as buildings, bridges, and dams. They can also trigger landslides.

 Some of the most visible effects of an earthquake are damage to buildings and roads and death. Other effects include broken gas lines, fires and in some cases a tsunami.

 The effects of earthquakes produce extreme damages. Some of the massive earthquake cause massive damage. For instance loss of property and lifestyles and deformed ground surfaces is also another damages with brings a country that has been affected to a stand still in development. Exposure to deep minerals and formation of new minerals is also an effect of earthquakes.

Direct Shaking Hazards and Human-Made Structures

Most earthquake-related deaths are caused by the collapse of structures and the construction practices play a tremendous role in the death toll of an earthquake. In southern Italy in 1909 more than 100,000 people perished in an earthquake that struck the region. Almost half of the people living in the region of Messina were killed due to the easily collapsible structures that dominated the villages of the region. A larger earthquake that struck San Francisco three years earlier had killed fewer people (about 700) because building construction practices were different type (predominantly wood). Survival rates in the San Francisco earthquake was about 98%, that in the Messina earthquake was between 33% and 45%) (Zebrowski, 1997). Building practices can make all the difference in earthquakes, even a moderate rupture beneath a city with structures unprepared for shaking can produce tens of thousands of casualties.

Although probably the most important, direct shaking effects are not the only hazard associated with earthquakes, other effects such as landslides, liquefaction, and tsunamis have also played important part in destruction produced by earthquakes.

Geologic Effects on Shaking

When we discussed earthquake intensity we discussed some of the basic factors that affect the amplitude and duration of shaking produced by an earthquake (earthquake size, distance from fault, site and regional geology, etc.) and as you are aware, the shaking caused by seismic waves can cause damage buildings or cause buildings to collapse. The level of damage done to a structure depends on the amplitude and the duration of shaking. The amplitudes are largest close to large earthquakes and the duration generally increases with the size of the earthquake (larger quakes shake longer because they rupture larger areas). Regional geology can affect the level and duration of shaking but more important are local site conditions. Although the process can be complicated for strong shaking, generally shaking in soft sediments is larger and longer than when compared with the shaking experienced at a "hard rock" site.

 

Preparing Structures for Shaking

The first step in preparing structures for shaking is to understand how buildings respond to ground motions- this is the field of study for earthquake and structural engineers.

When the ground shakes, buildings respond to the accelerations transmitted from the ground through the structure's foundation. The inertia of the building (it wants to stay at rest) can cause shearing of the structure which can concentrate stresses on the weak walls or joints in the structure resulting in failure or perhaps total collapse. The type of shaking and the frequency of shaking depends on the structure. Tall buildings tend to amplify the motions of longer period motions when compared with small buildings. Each structure has a resonance frequency that is characteristic of the building. Predicting the precise behavior of buildings is complicated, a rule of thumb is that the period of resonance is about equal to 0.1 times the number of stories in the structure. Thus Macelwane Hall resonates at about 0.3 seconds period, and Griesedeck at about 1.4 seconds.

Taller buildings also tend to shake longer than short buildings, which can make them relatively more susceptible to damage. Fortunately many tall buildings are constructed to withstand strong winds and some precautions have been taken to reduce their tendency to shake. And they can be made resistant to earthquake vibrations.

In many regions of limited resources and/or old structures, the structures are not very well suited to earthquake induced strains and collapse of adobe-style construction has caused thousands of deaths in the last decade. The worst possible structure for earthquake regions is the unreinforced masonry (which is common in the St. Louis area).

Estimating Hazards

Preparing structures (either new or old) for earthquakes is expensive and the level of investment is a social and political decision. The choice of building design is a compromise between appearance, function, structure, strength, and of course, cost. Standards are instituted through the establishment of Building Codes, which regulate the design and construction of buildings. Most of our building codes are designed to protect first the building occupants, and second the building integrity. Building codes are usually drafted to meet the demands of the expected shaking in a given region that are summarized by seismologists and earthquake engineers in hazards maps. Hazard maps are constructed by examining

The earthquake history of the region to estimate the probability of an earthquake

The expected shaking intensity produced by the earthquake (often expressed as a peak acceleration)

The frequency of the shaking, the distance from the fault The regional geology and site conditions

to estimate the maximum level of shaking expected during the lifetime of a building. Constructing accurate hazard maps is a challenge and remains the focus of much Geoscience research. For the Midwest you may want to check out the WWW site of a large multidisciplinary effort to help prepare the eastern US for the low-probability, but high consequence earthquake hazards (check out the Mid-America Earthquake Center).

(Courtesy of Dr. Robert Herrmann, Saint Louis University)

Strengthening Structures

We have two approaches for preparing buildings for earthquakes: you either secure the building components (walls, floors, foundation, etc.) together and have the entire structure behave as a single stiff unit that moves with the ground, or you construct a strong and flexible structure that distorts but doesn't break and absorbs some of the shaking energy. Either approach can be expensive so we cannot build all our structures to withstand the largest possible earthquake. We must make compromises and accept some risk (this is not unlike the risks that we accept every day, driving on a freeway, flying in an airplane, living in flood-prone regions, tornado "alley", hurricane-prone regions, etc.).

We need different levels of resistance for different classes of structures. Critical structures such as hospitals, power, water-treatment, and chemical plants, dams, etc. must not only survive the shaking, but must remain in operation. These structure require the largest investment of resources to insure that they can provide services following an earthquake.

More general requirements for other structure include having our buildings

Sustain little damage in small-to-moderate quakes (M < 5.5) Sustain some repairable damage for moderate quakes (5.5 < M < 7.0) Not collapse in large earthquakes (M > 7.0)

To insure that we meet these goals we can take a number of steps, beginning with thoughtful and responsible planning and zoning laws. Since we know that sites with soft, water-saturated foundations are prone to damage, we should resist the temptation to build on those sits and we should certainly not put critical structures on such sites, and avoid building on these sites at all if possible. If that's not possible, try to compact the soft sediments before the constructing or anchor the structure in the basement.

We can take a number of steps to strengthen buildings including using steel frame construction, adequately securing the structure to the ground through a solid foundation, incorporating shear walls and or cross-bracing into the structure, or more sophisticated approaches such as using rubber or steel pads to isolate the structure from the shaking.

We have talked above seismic waves and how they vibrate the ground which can lead directly to the collapse of structures. There are other, secondary effects that are caused by earthquakes, most often a result of strong shaking. A simple example common in many earthquakes are landslides. The shaking causes regions of the rock and soil to slide downhill. The same material would eventually fail with increased time, but earthquakes trigger many slides that do much bit of damage.

Landslides and Liquefaction

Buildings aren't the only thing to fail under the stresses of seismic waves. Often unstable regions of hillsides or mountains fail. In addition to the obvious hazard posed by large landslides, even non lethal slides can cause problems when they block highways they can be inconvenient or cause problems for emergency and rescue operations.

Occasionally large landslides can be triggered by earthquakes. In 1970 an earthquake off the coast of Peru produced a landslide than began 80 miles away from the earthquake. The slide was large (witnesses estimated it's height at about 30 meters or 100 feet), traveled at more than one-hundred miles per hour and plowed through part of one village and annihilated another, killing more than 18,000 people.

In some cases, when the surface is underlain by a saturated, sand rich layer of soil, prolonged shaking can cause the expulsion of fluid from the sand layer resulting in large "sand blows" that erupt through the overlying strata.

In the 1811-12 earthquakes the sand blows were enormous and covered large regions of the Missouri bootheel. Liquefaction can cause other problems as the soil loses it ability to resist shear and flows much like quick sand. Anything relying on the substrata for support can shift, tilt, rupture, or collapse.

 

 

Tsunamis

A sometimes dramatic byproduct of certain types of earthquakes are tsunamis. Tsunami is a Japanese term that means "harbor wave". Tsunamis are frequently confused with tidal waves, but they have nothing to do with the tides, they are the result of a sudden vertical offset in the ocean floor caused by earthquakes, submarine landslides, and volcanic deformation. In 1883 the volcanic eruption of Krakatoa resulted in the collapse of a caldera that initiated a tsunami which killed 36,000 people on nearby islands. On June 25, 1896 an earthquake off the Japanese coast generated a tsunami that hit the shore with wave heights ranging from 10 to 100 feet. As the fishing fleets returned to shore following an overnight trip they found their villages destroyed and 22,000 people dead. In the last century more than 50,000 people have died as a result of tsunamis.

Tsunami Initiation

A sudden offset changes the elevation of the ocean and initiates a water wave that travels outward from the region of sea-floor disruption. Tsunamis can travel all the way across the ocean and large earthquakes in Alaska and Chile have generated waves that caused damage and deaths in regions as far away as California, Hawaii and Japan.

Tsunamis are initiated by a sudden displacement of the ocean, commonly caused by vertical deformation of the ocean floor during earthquakes. Other causes such as deformation by landslides and volcanic processes also generate tsunamis.

The speed of this wave depends on the ocean depth and is typically about as fast as a commercial passenger jet (about 0.2 km/s or 712 km/hr). This is relatively slow compared to seismic waves, so we are often alerted to the dangers of the tsunami by the shaking before the wave arrives. The trouble is that the time to react is not very long in regions close to the earthquake that caused the tsunami.

In deep water tsunamis are not large and pose no danger. They are very broad with horizontal wavelengths of hundreds of kilometers and surface heights much much smaller, about one meter.

Tsunamis pose no threat in the deep ocean because they are only a meter or so high in deep water. But as the wave approaches the shore and the water shallows, all the energy that was distributed throughout the ocean depth becomes concentrated in the shallow water and the wave height increases.

When a tsunami approaches the shore, the water depth decreases, the front of the wave slows down, the wave grows dramatically, and surges on land.

Typical heights for large tsunamis are on the order of 10s of meters and a few have approached 90 meters (about 300 feet). These waves are typically more devastating to the coastal region than the shaking of the earthquake that caused the tsunami. Even the more common tsunamis of about 10-20 meters can "wipe clean" coastal communities.

Deadly tsunamis occur about every one to two years and they have at times killed thousands of people. In 1992-93 three large tsunamis occurred: one in Japan, Indonesia, and Nicaragua. All struck at night and devastated the local communities.

The 1946 Scotch Point Lightstation Tsunami

At 1:28AM, April 1, 1946, about 150 km (100 miles) south of Unimak Island in the Aleutians, a large earthquake offset the ocean floor and rattled a lightstation operated by five U. S. Coast Guard personnel. Unknown to the lightstation operators, the earthquake had also generated a large tsunami. It took about 50 minutes for the waves to travel across the shallow continental shelf and arrive at the lightstation at 02:18AM.

The weather was clear and calm and the five-story lightstation was about 32 feet above sea-level. The crew heard a large roar from the sea just before a 100-foot high tsunami struck and completely demolished the station killing all inside. At 7 AM, as survivors from a nearby station (located higher up the cliff but considerably damaged and evacuated when the waves hit) were searching for survivors, the tsunami arrived 2200 km at Hawaii away where a series of waves struck the islands killing 159 more people.