428Earthquakes

428Earthquakes - 1 Earthquakes Earthquakes Geography and cause of earthquakes and their risk assessment Definitions Definitions Earthquake a sudden

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Unformatted text preview: 1 Earthquakes Earthquakes Geography and cause of earthquakes and their risk assessment Definitions Definitions Earthquake : a sudden shaking and breaking of the earth Focus : the point within the earth where the earthquake starts Epicenter : the location on the earth surface directly above the focus Useful Web Sites Useful Web Sites • http://earthquake.usgs.gov/ • http://quake.wr.usgs.gov/prepare/factsheets/ RiskMaps/ • http://www.redcross.org/services/disaster/be prepared/ • http://www.fema.gov/library/prepandprev.s htm#earthquakes Depth Classification Depth Classification Shallow-focus 0-70 km deep Intermediate focus 70-300 km deep Deep focus 300-800 lm deep No earthquakes deeper than 800 km! Lithosphere Lithosphere • The rigid outer layer of the earth • 70 to 200 km thick • All earthquakes occur in the lithosphere Asthenosphere Asthenosphere • Lies under the lithosphere • Can not withstand shear stress • Undergoes aseismic creep 2 Lisa Wald USGS Pasadena U.S. Department of the Interior U.S. Geological Survey USGS Earthquake Hazards Program Earthquakes 101 (EQ101) Global Distribution of Earthquakes Seismic Waves Earthquake Location Locations of Seismic Activity Locations of Seismic Activity • Most earthquakes occur at plate boundaries (interplate) • A few earthquakes occur within plate interiors (intraplate) Lisa Wald USGS Pasadena U.S. Department of the Interior U.S. Geological Survey USGS Earthquake Hazards Program Plate Tectonics 3 Plate Boundaries Plate Boundaries • Accretionary boundary • Subduction boundary • Collision boundary • Transform boundary Accretionary boundary Accretionary boundary • Both sides move apart • New material is accreted along axis • Geomagnetic field is embedded recording polarity reversals • Example is Mid Atlantic Ridge Subduction Boundary Subduction Boundary • One plate subducted or pushed under another • Intermediate or deep earthquakes occur along the boundaries or within the subducting plate • Benioff Zone...
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This note was uploaded on 11/07/2011 for the course ECON 1129863 taught by Professor Stewart during the Spring '11 term at ENSEA.

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428Earthquakes - 1 Earthquakes Earthquakes Geography and cause of earthquakes and their risk assessment Definitions Definitions Earthquake a sudden

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