intro tsunami

8/13/2019 Intro Tsunami

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Natural Disaster

TSUNAMI


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Introduction

A natural disaster is the consequence of thecombination of a natural hazard (a physicalevent e.g. volcanic eruption, earthquake,

landslide, flood, tornado, hurricane etc.) andhuman activities.

This understanding is concentrated in theformulation: "disasters occur when hazards

meet vulnerability.


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Natural disasters

1 Geological disasters

1.1 Avalanches

1.2 Earthquakes

1.3 Volcanic eruptions (S.C.S)

2 Hydrological disasters

2.1 Floods

2.2 Limnic eruptions

2.3 Tsunamis 3 Fires
http://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disaster


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4 Meteorological disasters 3.1 Blizzards

3.2 Cyclonic storms

3.3 Droughts

3.4 Hailstorms 3.5 Heat waves

3.6 Tornadoes

5 Health disasters

6 Space disasters 6.1 Impact events

6.2 Solar flares

6.3 Gamma ray burst
http://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disasterhttp://en.wikipedia.org/wiki/Natural_disaster


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Tsunami

A tsunami is a wave train, or series of waves,generated in a body of water by an impulsivedisturbance that vertically displaces the watercolumn.

Earthquakes, landslides, volcanic eruptions,explosions, and even the impact of cosmic bodies,such as meteorites, can generate tsunamis.

Tsunamis can savagely attack coastlines, causingdevastating property damage and loss of life.


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How do tsunamis differ from other water

waves?

Tsunamis are unlike wind-generated waves, whichmany of us may have observed on a local lake or at acoastal beach, in that they are characterized as

shallow-water waves, with long periods and wavelengths.

Wind-generated waves have a period of about 10seconds and a wave length of 150 m. A tsunami, on

the other hand, can have a wavelength in excess of100 km and period on the order of one hour


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Regular Wind Generated Wave

10 Feet

300 Feet

Speed: 10-20 mph


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Tsunami in Deep Ocean

1-2 Feet

316,800 Feet

Speed: 450-650 mph


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Generation mechanisms

The principal generation mechanism of a tsunami isthe displacement of a substantial volume of water orperturbation of the sea. This displacement of water isusually attributed to either earthquakes, landslides,

volcanic eruptions, glacier calving or more rarely bymeteorites and nuclear tests. The waves formed in this

way are then sustained by gravity.

Earthquakes

Volcanoes Landslides

Asteroids


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12


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The deeper the waterthe faster it is

In the shallowwater

The bigger it is


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Tectonic quake casuethe most destructiveand common tsunamis;

When a quake iscolossal, at least 7.5 inmagnitude, it displacesenough water to case ahuge wave;

Such quakes oftenoccurs at a thrust fault.

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Earthquake cause Tsunamis contd.

Past Earthquakes and Tsunamis in the IndianOceannote the magnitude of the 1883 and 2004

earthquakes/tsunamis


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Volcanoes cause Tsunami15

A classic aboveground eruption can disturb theocean floor and generate a tsunami.


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Volcanoes Contd.16

submarine events likeeruptions, cascades of ash orthe collapse of a volcanicflank, can also be the cause

of a tsunami. In 1883, thevolcanic eruption ofKrakatau and the collapse ofits caldera stirred up 130-

foot high waves and killed36,000 people.


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Landslides Cause Tsunami17

Usually set off by

Earthquakes or

Rock and icefalls

Highest such wave was recorded in Lituya Bay,Alaska in 1958: a quake-triggered rock fall threw upa 500+m wave.

Scientists discovered that extremely large landslidesfrom volcanic island collapses can generatemegatsunamis that can cross oceans.


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Landslides Contd.19

In the 1950s, it was discovered that larger tsunamisthan had previously been believed possible could becaused by giant landslide.

Underwater landslides that generate tsunamis are

called sciorrucks.These phenomena rapidly displacelarge water volumes, as energy from falling debris orexpansion transfers to the water at a rate faster thanthe water can absorb. Their existence was confirmed

in 1958, when a giant landslide in Lituya bay, Alaskacaused the highest wave ever recorded, which had aheight of 524 mtrs.


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Landslides Contd.20

The wave didn't travel far, as it struck land almostimmediately. Two people fishing in the bay werekilled, but another boat amazingly managed to ridethe wave. Scientists named these wavesMegatsunami.

Scientists discovered that extremely large landslidesfrom volcanic island collapses can generate

megatsunamis that can cross oceans.


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Asteroids cause tsunami21

35 million years ago an asteroid blasted an 80 kmwide crater under what is now the southern tip ofChesapeake Bay. The resulting waves are known tohave roared inland for hundreds of miles!

ChesapeakeBay


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Contd.22

Artists impression of the impact of an asteroid onEarth an asteroid of a few kilometers in diametermay release as much energy as several millionnuclear bombs detonating!


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Characteristics23

Tsunamis cause damage by two mechanisms: thesmashing force of a wall of water travelling at highspeed, and the destructive power of a large volume of

water draining off the land and carrying all with it,even if the wave did not look large.

While everydaywind waveshave awavelength(fromcrest to crest) of about 100 metres (330 ft) and a

height of roughly 2 metres (6.6 ft), a tsunami in thedeep ocean has a wavelength of about 200kilometres (120 mi).
http://en.wikipedia.org/wiki/Wind_wavehttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Wind_wave


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Such a wave travels at well over 800 kilometers per hour(500 mph), but owing to the enormous wavelength the

wave oscillation at any given point takes 20 or 30minutes to complete a cycle and has an amplitude of only

about 1 metre (3.3 ft). This makes tsunamis difficult todetect over deep water. Ships rarely notice their passage.

As the tsunami approaches the coast and the watersbecome shallow,wave shoalingcompresses the wave and

its velocity slows below 80 kilometres per hour (50 mph).Its wavelength diminishes to less than 20 kilometres(12 mi) and its amplitude grows enormously.
http://en.wikipedia.org/wiki/Wave_shoalinghttp://en.wikipedia.org/wiki/Wave_shoaling


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25

Since the wave still has the same very long period,the tsunami may take minutes to reach full height.

Except for the very largest tsunamis, the

approaching wave does notbreak, but rather appearslike a fast-moving tidal bore.[23]Open bays andcoastlines adjacent to very deep water may shape thetsunami further into a step-like wave with a steep-

breaking front
http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Breaking_wavehttp://en.wikipedia.org/wiki/Tidal_borehttp://en.wikipedia.org/wiki/Tsunamihttp://en.wikipedia.org/wiki/Tsunamihttp://en.wikipedia.org/wiki/Tidal_borehttp://en.wikipedia.org/wiki/Breaking_wavehttp://en.wikipedia.org/wiki/Frequency


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Drawback26

If the first part of a tsunami to reach land is atroughcalled a drawbackrather than a wavecrest, the water along the shoreline recedesdramatically, exposing normally submerged areas.


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A drawback occurs because the water propagatesoutwards with the trough of the wave at its front.Drawback begins before the wave arrives at aninterval equal to half of the wave's period. Drawbackcan exceed hundreds of metres, and people unawareof the danger sometimes remain near the shore tosatisfy their curiosity or to collect fish from theexposed seabed.


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Scales of intensity and magnitude28

Intensity scales

The first scales used routinely to measure theintensity of tsunami were theSieberg-Ambraseys

scale, used in the Mediterranean Sea,theImamura-Iida intensity scale, used in thePacific Ocean.

The latter scale was modified by Soloviev, whocalculated the Tsunami intensityIaccording to the

formula
http://en.wikipedia.org/wiki/Mediterranean_Seahttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Mediterranean_Sea


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Contd.29

whereHavis the average wave height along thenearest coast. This scale, known as theSoloviev-

Imamura tsunami intensity scale, is used in theglobal tsunami catalogues compiled bythe NGDC/NOAAand the Novosibirsk TsunamiLaboratory as the main parameter for the size of thetsunami.
http://en.wikipedia.org/wiki/NGDChttp://en.wikipedia.org/wiki/NOAAhttp://en.wikipedia.org/wiki/NOAAhttp://en.wikipedia.org/wiki/NGDC


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Magnitude scales30

The first scale that genuinely calculated a magnitudefor a tsunami, rather than an intensity at a particularlocation was the ML scale proposed by Murty &Loomis based on the potential energy.Difficulties incalculating the potential energy of the tsunami meanthat this scale is rarely used. Abe introducedthe tsunami magnitude scale Mt, calculated from,


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Contd.31

where his the maximum tsunami-wave amplitude(in m) measured by a tide gauge at a distanceRfromthe epicenter, a, b&Dare constants used to makethe M

t

scale match as closely as possible with themoment magnitude scale.


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Warnings and predictions32

Drawbacks can serve as a brief warning.

People who observe drawback (many survivorsreport an accompanying sucking sound), can survive

only if they immediately run for high ground or seekthe upper floors of nearby buildings.

Tsunami Warning Sign ->


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Tsunami Cycle

TidalSurge

UnderlyingGeologicalEvent

WaterDisplaced

WavePropagation

TidalWithdraw

DetectionOpportunities


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Detection

CoastlineActivity

WaveActivity

GeologicActivity

Phase 1 Phase 2 Phase 3


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Current State of the Art

5,000 M

Surface Buoy

Hydrophone

Anchor

TsunamiDetector

Acoustic Link

Satellite

Gonzalez, F.I. (1999): Tsunami!. Scientific American, 280(5), 56-65


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Genesis Tsunami Coastal Alert

Anchor

Tsunami troughthreshold level

Receding seatrigger

Anchor lineunder constantspring tension atbuoy


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Anchor

Tsunami troughthreshold level

Tsunami trough(receding sea)

Tension inanchor line pullsbuoy into contactwith trigger

Flares ignited tosignal coastalcommunities

Satellite, RF, audible alarmsexecute responsive to contactwith trigger


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Buoy measures tsunami crestbroadcasts satellite data foremergency response in otherareas.


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Advantages & Drawbacks

Advantages Deep water pressure

produces relatively low false-positives as wind-drivenwaves do not generate deep

pressure differentials

Multiple sensors cantriangulate epicenter ofwater displacement and wavepropagation can be

predicted.

Good advance warning

Drawbacks Expensive equipment

High maintenance

Requires multiple

communication links: Sonar

Satellite uplink

Satellite downlink

Last-mile notification to

authorities Authorities must notify coastal

dwellers


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Deep sea pressure

SeismicEvents

Surface anomalies

CoastalAlarm &Detection


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Genesis Tsunami Offshore Alert

Detachablepressure sensors

Pressure changesbelow predetermined

depth are indicators oftsunami activity.NOAAs DART system usespressure sensors that arepermanently mounted to seabed.Prone to failure.


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Pressure changesbelow predetermineddepth are indicators oftsunami activity.

Seismic event detected Genesis Offshore buoys droppressure sensors to multipledepths.

Pressure Wave


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Pressure changesbelow predetermineddepth are indicators oftsunami activity.

Pressure readings are relayedto monitoring station. Multiplereadings provide more accurateanalysis of deep pressure

readings.

Satellite


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Genesis Drop Sensor

Lead weight is adjusted so thatrate of decent is controlled sothat multiple sensors reachtheir operating depth insynchronization.

Sensor is maintained abovewaterline before release. Nofouling or damage from deepsea mounting.

Pressure transducer suppliedby Paroscientific, Inc. Quartzcrystal detection of flex ofBourdon tube.

Telemetry and

support line.


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intro tsunami

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