earthquake hazard

Department of Earth SciencesKFUPM

Introduction to Seismology

Earthquake Hazard

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Ali [email protected].

sa

33° E 60° E

10° N

37°N

Through the e-mail

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Previous Quiz

m

(3)

(1)

(2)

(1) Explain the physical meaning of above graph?(2) What you think might be a reason for observing

roll-off at lower (3) and higher (1) magnitudes.

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Log N

Natural hazards in time

Magnitude

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GEOL 3026/C471 GEOLOGICAL HAZARDS2005

Geological hazards in context II: fatalities worldwide 2000

Quake & volcano 4%

Total 9,270

Flood 67%Windstorm 15%

Other 14%

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Example: Seismicity of Stable Craton Cores (SCC) •Earthquake Catalogue Completeness for SCC •Magnitude Range for SCC •Magnitude-Frequency Plot for SCC •Worldwide rates of stable cratonic core seismicity

•African SCC seismicity •North American SCC seismicity •South American SCC Seismicity •Australian SCC Seismicity

•Seismicity of Canadian Stable Craton •Seismicity of Arabian Stable Craton

Previous LectureIn

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Spatial distribution of hazards

Principal earthquake zones and explosivevolcanoes

‘Ring of Fire’

S. E. Asia

CaribbeanMountSt. Helens1980

Montserrat1995-present

Toba 73ka

Pinatubo 1991

Tambora 1815

Aitapei1998

Alaska 1964

Northridge 1994Loma Prieta 1989

Chile 1960

Izmit 1999Lisbon1755

Tangshen1976

Tokyo 1923Kobe 1995

Tropical cyclone zones

Bhuj 2001

Taiwan 1999

Columbia 1999

Venezuela 2000Hurricane Mitch1999



Quake & volcano 4%

Total 9,270


Other 14%

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Where do earthquakes occur?

Alaska 1964

Chile 1960

Tokyo 1923Kobe 1995

Turkey 1999Lisbon1755

The 20th C top ten

California1989 1994

Gujarat2001

Kashmir2005

Sumatra2004



Quake & volcano 4%

Total 9,270


Other 14%

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SEISMIC HAZARD AND RISK

Earthquake quantificationSo far: how big?

ML, mb, Ms, Mw

how much damage? I, Io, I MSK, I MM

where?WWSSN, local networks, ISC

and now: when?earthquake prediction

how often?seismic or earthquake

hazard

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The probability of an earthquake occurring:•Specifically: the probability of an earthquake of magnitude m occurring or being exceeded

or•the probability of ground motion at level x occurring or being exceeded (where x = I, a, v or d)

Seismic hazard and Risk

Seismic risk $ RISK = HAZARD x VULNERABILITY x $ VALUE (Unesco)

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IDNDR OfficeIn

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Earthquakes as a hazard

Estimated > 8 million killed in earthquakes during last millennium2 million deaths in 20th century1990-99 cost US$215 billionOver 40 countries are under threat from major destructive quakesOver 100 a year have potential for serious destruction (>M = 6)

Source: USGS

1,300,000 est2 – 2.9Very minor

130,000 est3 – 3.9Minor

13,000 est4 – 4.9Light

13195 – 5.9Moderate

1346 – 6.9Strong

177 – 7.9Major

18 and aboveGreat

ANNUAL AVERAGE

MAGNITUDE

1,300,000 est2 – 2.9Very minor

130,000 est3 – 3.9Minor

13,000 est4 – 4.9Light

13195 – 5.9Moderate

1346 – 6.9Strong

177 – 7.9Major

18 and aboveGreat

ANNUAL AVERAGE

MAGNITUDE

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Some notable earthquakes in history

Source: Hazard Research Center

Year Region Deaths Magnitude (Ms) 1556 China (Shensi) 830,000 - 1737 India (Calcutta) 300,000 1811 US (Missouri, New Madrid) several Mercalli intensity XI 1819 India (Kutch) 1,543 1906 US (California, San

Francisco) 700 8.25

1908 Italy (Messina) 120,000 7.5 1920 China (Kansu) 180,000 8.5 1923 Japan (Tokyo-Yokohama) 143,000 8.2 1960 Southern Chile > 3,000 8.5 1964 Alaska 131 8.6 1976 China (Tangshan) > 250,000 7.6

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Recent notable earthquakes

Year Region Deaths Magnitude (Ms) 1989 US/California (Loma Prieta) 63 7.0 1989 Newcastle (Australia) 13 5.6 1994 US/California (Northridge) 56 6.9 1995 Kobe (Japan) 5,400 6.9 1999 Izmit (Turkey) ~19,118 7.4 1999 Chi-chi (Taiwan) 3,400 7.6 1999 Athens (Greece) 110 5.9 2001 Gujarat (India) ~100,000? 7.6 2004 Niigata (Japan) 35 6.6 2004 Sumatra (Indonesia) 300,000? 9.15m

2005 Kashmir (Pakistan) ~ 80,000 7.6 Source: Hazard Research Center

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Yearly average of worldwide damage from natural disasters in the last three decades (data from Munich R)

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Geological hazards in context:loss events worldwide 2000

Windstorm38%

Others 26%

Earthquake & volcanic14%

Flood22%Total 851

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Quake & volcano 4%

Total 9,270


Other 14%

Source


Quake & volcano 4%

Total 9,270


Other 14%

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Quake & volcano 4%

Total 9,270


Other 14%

Source

Geological hazards in context III: economic losses worldwide 2000

Flood 53%Quake & volcanic 1%

Other 14%

Windstorm 32%Total US$ 31 bn

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Quake & volcano 4%

Total 9,270


Other 14%

Source

Geological hazards in context IV: insured losses worldwide 2000

Windstorm 75%Other 4%

Flood 21%

Total US$ 8.3 bn

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Quake & volcano 4%

Total 9,270


Other 14%

Source

WHAT ARE WE TRYING TO ACHIEVE?

Scientifically-study seismicity properties of earthquake sequences cumulative coseismic deformation maximum earthquakes

Socially- mitigate against earthquake losses•advise land-use planners•advise decision makers•advise insurers•advise earthquake engineers and constructors

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In general terms:

estimate hazard-forecasting, time distribution

zone or macrozone -space distributionmicrozone - local fluctuations

define design earthquakesselect time histories ( seismograms)what is the maximum earthquake?what is the maximum loading during EQ?What is the lifetime of structure?What is design spectra like?what is the maximum credible loading?

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Forecasting earthquakesForecasting is not prediction

less precise based upon analysis of earthquake return periods rather than identification of pre-cursor y signs

Active faults or fault segments do not rupture in a random manner

they have characteristic return periods (or at least return period envelopes)these reflect strain accumulation along the fault and the capacity of the fault to resist strain up to a given characteristic point - for that fault or fault segment

There are complications:Rupture will not occur according to a rigid timetable - there is a return period envelope rather than specific dateStrain may be released by one large quake or a number of smaller ones (e.g. Marmara Sea south of Istanbul)this has implications for risk assessment



Quake & volcano 4%

Total 9,270


Other 14%

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The Seismic Gap concept

Defined as an area in an earthquake-prone region where there has been a below average level of seismic energy releaseThe 1989 Loma Prieta quake filled a gap that had been aseismic since 1906 Other gaps exist in

Aleutian arc (Alaska)south of IstanbulTokyosouthern California

Istanbul seismic gap

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Quake & volcano 4%

Total 9,270


Other 14%

Source

earthquake hazard

Technology