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Earthquakes

Earthquakes. And their impact on the lithosphere. Earthquakes. What is an Earthquake. General Information. Powerful Earthquake Reported in Costa Rica - YouTube. Over 30,000 happen each year worldwide that are strong enough to be felt

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Earthquakes

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  1. Earthquakes And their impact on the lithosphere

  2. Earthquakes What is an Earthquake

  3. General Information Powerful Earthquake Reported in Costa Rica - YouTube • 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

  4. 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

  5. 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

  6. Faults • Faults – fractures in earth’s crust and mantle where movement has occurred

  7. Cause of Quakes Earthquakes - Shock Waves Explained - YouTube • Elastic rebound hypothesis – explanation for the release of energy stored in deformed rocks

  8. Elastic Rebound Hypothesis How Earthquakes Work - YouTube • Rocks are in the original position • Stress builds up due to tectonic forces • Builds energy • Energy is released • Earthquake • Land rebounds into new position

  9. Aftershocks • Aftershocks – movements that follow a major earthquake • Sometimes destroy structures weakened by the quake

  10. Foreshocks • foreshocks - Small earthquakes happening before the major quake • Can be felt days or even years before

  11. Earthquakes Measuring Earthquakes

  12. Seismographs • Instruments that record earthquake waves

  13. Earthquake waves • 2 types • Surface waves • Body waves seismic waves - YouTube

  14. 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

  15. 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

  16. 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

  17. Earthquake zones

  18. Measuring earthquakes • 2 types of measurement • Intensity • Amount of shaking based on damage • qualitative • Magnitude • Calculations of energy released using seismographs • Quantitative

  19. 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

  20. 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

  21. Earthquakes Destruction from earthquakes

  22. Damage to buildings • Depends on several factors • Intensity and duration • Nature of the material on which the structure is built • Design of the structure

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

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