What is an Earthquake Over 30,000 happen each year worldwide that are strong enough to be felt ...
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![Page 1: What is an Earthquake Over 30,000 happen each year worldwide that are strong enough to be felt Only about 75 major earthquakes take place each year.](https://reader035.fdocuments.us/reader035/viewer/2022062314/56649dd35503460f94ac9ad6/html5/thumbnails/1.jpg)
EarthquakesAnd their impact on the lithosphere
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Earthquakes
What is an Earthquake
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General Information
Over 30,000 happen each year worldwide that are strong enough to be felt
Only about 75 major earthquakes take place each year many in remote regions
Powerful Earthquake Reported in Costa Rica - YouTube
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What is an Earthquake
A vibration of the Earth produced by the rapid release of energy
Caused by slippage along a break in Earth’s crust
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Focus and Epicenter
Focus – point within earth where the earthquake starts› Waves are produced here
Epicenter – location on the surface of Earth directly above the focus
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Faults
Faults – fractures in earth’s crust and mantle where movement has occurred
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Cause of Quakes
Elastic rebound hypothesis – explanation for the release of energy stored in deformed rocks
Earthquakes - Shock Waves Explained - YouTube
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Elastic Rebound Hypothesis
Rocks are in the original position
Stress builds up due to tectonic forces› Builds energy
Energy is released › Earthquake
Land rebounds into new position
How Earthquakes Work - YouTube
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Aftershocks
Aftershocks – movements that follow a major earthquake› Sometimes
destroy structures weakened by the quake
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Foreshocks
foreshocks - Small earthquakes happening before the major quake› Can be felt days or even years before
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Earthquakes
Measuring Earthquakes
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Seismographs
Instruments that record earthquake waves
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Earthquake waves
2 types› Surface waves› Body waves
seismic waves - YouTube
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Surface waves
Travel along earths outer layer
Up and down as well as side to side motion
Especially damaging to buildings
Slower than body waves
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Body waves
Pass through earth’s interior
P waves – push – pull or compression waves› Faster than S waves
S waves – shake particles at right angles› Cannot pass through
gases or liquids
S and P waves - YouTube
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Locating earthquakes
Seismographs can be used to see the difference in velocity between p and s waves
Interval between 1st p wave arrival and 1st s wave arrival › Longer the interval the further
the distance from the earthquake
Uses 3 or more seismographs
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Earthquake zones
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Measuring earthquakes
2 types of measurement› Intensity
Amount of shaking based on damage
qualitative› Magnitude
Calculations of energy released using seismographs
Quantitative
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Richter scale
Based on amplitude of largest seismic wave
Logarithmic› 10 fold increase in
wave amplitude of 1 on the magnitude scale 5.0 is 10X greater
than 4.0 Familiar but
outdated
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Moment magnitude
Based on amount of displacement at a fault zone
More precise Many different factors
› Av. amount of movement› Area of surface break› Strength of broken rock
Most widely used because it measures amount of energy released
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Earthquakes
Destruction from earthquakes
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Damage to buildings
Depends on several factors› Intensity and duration› Nature of the material on which the
structure is built› Design of the structure
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Liquefaction
Where loosely consolidated sediments are saturated with water, stable soil can turn to a liquid during earthquakes
Buildings may settle and collapse
Underground storage tanks and sewage lines may float to the surface
liquefaction
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Tsunamis
Destructive waves› Aka tidal waves
Not actually anything to do with tides Slab of ocean floor is displaced vertically
along a fault Or when a quake sets off an underwater
landslide
Japan Tsunami first wave ground footage - YouTube
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Other Dangers
Landslides – do the greatest damage› Soil and / or rock slopes fail
Fire – gas and electrical lines may be cut › when water lines are also cut, fires cannot
be stopped – San Francisco 1906
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Resources http://
www.bing.com/images/search?q=earthquakes&view=detail&id=EE1FD8ED426AAF3B77312E9A9484D8B0658EAC20&first=1
http://www.bing.com/images/search?q=earthquakes&view=detail&id=0728B2E8AF7D936E47C7BF9A02B44B97B405CF78&first=1
http://www.bing.com/images/search?q=earthquakes+fault&view=detail&id=FA2489321AD8DF470812AF17BE0995E91DC3A1C6
http://www.bing.com/images/search?q=earthquakes+fault&view=detail&id=40D683DDF14E595D6D4E9C9CF4E6F0AF6CD34876
http://www.bing.com/images/search?q=focus+and+epicenter&view=detail&id=FB2A1080B026570F0D431369A72135CFDE80F499
http://www.bing.com/images/search?q=focus+and+epicenter&view=detail&id=5946B7F86F88FEDF8AEAAF8D365662ADEA32DC7B
http://www.bing.com/images/search?q=faults+in+layers+of+earth&view=detail&id=36DC8F18B91F95FB51F5D6AE26A6B8989CFA9262
http://geology1a-1.wikispaces.com/file/view/af1-2.jpg/91060621/af1-2.jpg
http://www.bing.com/images/search?q=elastic+rebound+hypothesis&view=detail&id=324E2B8DBD877E7D1F275E3EA579513E54AD1B37
http://www.bing.com/images/search?q=elastic+rebound+hypothesis&view=detail&id=7062BC2EA8C716E24F9C497D66852D25DBBCCF7C
http://www.bing.com/images/search?q=aftershocks&view=detail&id=8853BBAD1093CE083BA03EACCF30069118E4964F
http://www.bing.com/images/search?q=foreshocks&view=detail&id=D1940E7C9DDB185FE9A0627D885B1E22587545B8
http://www.bing.com/images/search?q=chinese+seismograhs&view=detail&id=E40AAF20E3AAFDF2518CF57BF82D246432021C20
http://www.bing.com/images/search?q=chinese+seismograhs&view=detail&id=83C14F9337C971D280DD7DBB312D5330507EE293
http://www.bing.com/images/search?q=seismographs&view=detail&id=CBCC79FBD4D64BC13E8303C4A3ECA227DCA919A3
http://www.bing.com/images/search?q=waves+of+earthquakes&view=detail&id=AEC862B742E9419C10F2E533EEBE78AABEA7FDC9
http://www.bing.com/images/search?q=waves+of+earthquakes&view=detail&id=33B413C8FEF8F53B2FAFAB1313C2C8A33A1801D2
http://www.sciencephoto.com/image/167086/530wm/E3600021-P_and_S_seismic_body_waves,_artwork-SPL.jpg
http://www.bing.com/images/search?q=s+waves+and+p+waves&view=detail&id=D48D39E039FEEE7140C63325836489C38C9C614F
http://www.bing.com/images/search?q=locating+quakes&view=detail&id=03AD9F4CEADBC08D30ECFFBA469757A1B281DBB1
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More resources http://
www.bing.com/images/search?q=earthquake+zones&view=detail&id=A3F9FB5A69E1D039843C525F1BAF88159C66E083
http://www.bing.com/images/search?q=measuring+earthquakes&view=detail&id=B0094EED325431622BDF19EFA2AFAD11E44F9666
http://www.bing.com/images/search?q=richter+scale&view=detail&id=68579F29E8CD762823EC891EB5C8794EC51EA709
http://www.bing.com/images/search?q=moment+magnitude&view=detail&id=4D878897FBCA6B4E3805C8047D0365FAFAC739BB
http://www.bing.com/images/search?q=earthquake+damage+to+buidlings&view=detail&id=F5E5C8B45E5F45F6F091631C2EC236065EEFC0CD
http://www.bing.com/images/search?q=charleston+earthquake+bolts&view=detail&id=4C0D502CDE305E8C0BEE8908E67832D33E95ABC7
http://www.bing.com/images/search?q=liquefaction&view=detail&id=4EC6832420397B19256452B646F02EB09D096D33
http://www.bing.com/images/search?q=liquefaction&view=detail&id=328A257C25776AD3AF663F9412F83BF7E34EC497
http://www.bing.com/images/search?q=tsunami&view=detail&id=C188859273F9A8265A46DCF056BE058E9568162C
http://www.bing.com/images/search?q=tsunami&view=detail&id=9038EBFBAC6EE01E540C37E623206AE422AB9A39&first=119
http://www.bing.com/images/search?q=earthquake+landslides&view=detail&id=1B54A1285A4A2D03E769A8F49A2E86E26F1E4F84
http://www.bing.com/images/search?q=earthquake+fires&view=detail&id=979D85852B95F1347D623BFE9D2728FDAF28FD42