Lecture9 Earthquake Hazards

8/12/2019 Lecture9 Earthquake Hazards

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Earthquake Hazards

Lecture-9


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About 500,000 quakes occur every year. About 100

are potentially dangerous (in excess of Richter

Magnitude 6)

On average there are about 2 major quakes occur

annually - in excess of magnitude 8

Very large quakes occur perhaps once a decade - but

release nearly all the Earths seismic energy

Over 90% of the seismic energy released between

1900 & 1975 was released by 10 great quakes

Tectonic hazards: earthquakes


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List of Major Historic Earthquakes

Year Location Deaths Magnitude

1556 China 5,30,000 8.0

1906 San Francisco 700 7.9

1960 S. Chile 2,230 9.5

1964 Alaska 131 9.2

1976 China 7,00,000 7.81985 Mexico City 9,500 8.1

1989 California 62 7.1

1995 Kobe 5,472 6.9

2001 Gujarat, India 1,00,000 6.9

2004 Sumatra, Indonesia 2,30,210 9.3

2005 Pakistan 75000 7.6

2010 Haiti 46,000- 316,000 7.0

2011 Japan 15760 9.0


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7.8

8

8.2

8.4

8.6

8.8

9

9.2

9.4

9.6

1900 1920 1940 1960 1980 2000 2020

Magnitude

Year

Great (M > 8) Earthquakes Since 1900

Chile1906

List of major historic earthquakes


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Over 40 countries are under threat from majordestructive quakes

The biggest losses occur where major quakes coincide

with concentrations of people and structures

Kobe earthquake in the year 1999 resulted ineconomic losses of US$ 200 bn

Gujarat earthquake in the year 2001 may have killed

over 100,000

Tectonic hazards: earthquakes


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Tectonic hazards: Critical issues

Seismic risk maps are not available for many regions All earthquakes do not occur along plate boundaries

We have not reached a stage to predict the date and

location of earthquake

Vulnerability to earthquakes is increasing dramatically

Increasing urbanization is resulting in more damages


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Where do earthquakes occur?

Source: wikipedia


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Major Earthquake Hazards

Ground Motion: Shakes the structures and damages themor causes them to collapse

Liquefaction: Happens in loose saturated cohesionless

soils in which the firm soil is converted into a fluid which

has no shear strength and structures found on these soilsfail due to loss of bearing capacity of the ground

Landslides: Vibrations during earthquake trigger large

slope failures

Fire : Indirect result of earthquakes triggered by brokengas and power lines

Tsunamis: large waves created by the instantaneous

displacement of the sea floor during submarine

earthquakes


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Size of quake

Distance from epicenter

Depth of quake

Duration of shaking

The local geology

Meteorological

conditions

Construction

Building code

enforcement

What determines the destructiveness of a

quake?

Earthquake damage in downtown Port-au-

Prince (Source: wikimedia)


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Frequency of shaking differs for different seismic waves.

High frequency body waves shake low buildings more.

Low frequency surface waves shake high buildings more.

Intensity of shaking also depends on type of subsurface material.Unconsolidated materials amplify shaking more than rocks do.

Buildings respond differently to shaking depending on theconstruction styles and materials

-Wood is more more flexible, holds up well

-Earthen materials, unreinforced concrete are veryvulnerable to shaking.

Earthquake Destruction: Ground Shaking


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Collapse of Buildings

Image of Bachau in Kutch region of Gujarat after earthquake


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Bui lding design: Bui ldings that are not designed for

earthquake loads suffer more

Image of a collapsed building in Ahmedabad during Bhuj earthquake


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Causes failure of lifelines

Source: google images


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Annual Landslide Costs

0 1 2 3 4

Japan

Italy

USA

India

China

Ex USSR

Spain

Canada

Sweden

New Zealand

NorwayCountry

Annual Landslide Cost (1990 US$ Billion)

Global: US$ 10-20 Billion

Source: wikipedia


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Earthquake Destruction: Liquefaction

Buildings founded on saturated cohesionless

soils are vulnerable

Nigata, JAPAN 1964

Source: http://www.ce.washington.edu


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Sand Boil: Ground water rushing to the surface due to

liquefaction

Sand boils in Gujarat earthquake


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Sand boils that erupted during the 2011 Canterbury earthquake, New Zealand.

Source: wikipedia


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Lateral Spreading: Liquefaction related phenomenon

Fissures caused by lateral spreading during Haiti earthquake

Source: wikipedia


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Lateral spreading in the soil beneath embankment causes the

embankment to be pulled apart, producing the large crack down thecenter of the road.

Cracked Highway, Alaska earthquake,

1964



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Liquefied soil exerts higher pressure on retaining

walls,which can cause them to tilt or slide.



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Increased water pressure causes collapse of dams

Source: wikipedia


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Earthquake Destruction: Fire

Earthquakes sometimes causefire due to broken gas lines,

contributing to the loss of life

and economy.

The destruction of lifelines and

utilities make impossible forfirefighters to reach fires started and

make the situation worse

eg. 1989 Loma Prieta

1906 San Francisco

2011 JapanSource: International Business Times


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Earthquake Destruction: Fire

Northridge, 1994

Source: wikimedia


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Tsunami Movement: ~600 mph in deep water

~250 mph in medium depth water

~35 mph in shallow water

Earthquake Destruction: Tsunami

Source: USGS public domain


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At least 1500 (possibly

~3000) active volcanoes Around 50 erupt annually

Over 82,000 people killed in

20th century

Two eruptions killed over

20,000

500 million people

threatened

Perhaps 150 volcanoes

monitored

Earthquake Destruction: Volanoes

Etna (Sicily)Source: wikipedia


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Earthquake Destruction: Volanoes


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Geomorphological changes are often caused by anearthquake: e.g., movements--either vertical or horizontal--

along geological fault traces; the raising, lowering, and tilting of

the ground surface with related effects on the flow of

groundwater;

An earthquake produces a permanent displacement across

the fault.

Once a fault has been produced, it is a weakness within the

rock, and is the likely location for future earthquakes.

After many earthquakes, the total displacement on a large

fault may build up to many kilometers, and the length of the

fault may propagate for hundreds of kilometers.

Geomorphological Changes


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Kramer (1996) Geotechnical Earthquake Engineering, Prentice Hall.

Robert W. Day (2002) Geotechnical Earthquake Engineering Handbook

McGraw-Hill.

http://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-

Hazards(Accessed on 27 March 2012)

http://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter7

EarthquakeHazards.pdf(Accessed on 27 March 2012)

Timothy M. Kusky (2008). Earthquakes: Plate Tectonics and Earthquake

Hazards, Facts on file.

References
http://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter7EarthquakeHazards.pdfhttp://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter7EarthquakeHazards.pdfhttp://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter7EarthquakeHazards.pdfhttp://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter7EarthquakeHazards.pdfhttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazardshttp://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquake-Hazards

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Lecture9 Earthquake Hazards