lecture9 earthquake hazards
TRANSCRIPT
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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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8
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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Earthquake Destruction: Ground Shaking
Collapse of Buildings
Image of Bachau in Kutch region of Gujarat after earthquake
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Earthquake Destruction: Ground Shaking
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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Earthquake Destruction: Ground Shaking
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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Earthquake Destruction: Liquefaction
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Earthquake Destruction: Liquefaction
Sand Boil: Ground water rushing to the surface due to
liquefaction
Sand boils in Gujarat earthquake
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Earthquake Destruction: Liquefaction
Sand boils that erupted during the 2011 Canterbury earthquake, New Zealand.
Source: wikipedia
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Earthquake Destruction: Liquefaction
Lateral Spreading: Liquefaction related phenomenon
Fissures caused by lateral spreading during Haiti earthquake
Source: wikipedia
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Earthquake Destruction: Liquefaction
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
Source: google images
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Earthquake Destruction: Liquefaction
Liquefied soil exerts higher pressure on retaining
walls,which can cause them to tilt or slide.
Source: google images
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Earthquake Destruction: Liquefaction
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