EQ-lect9_6_

EQ-lect9_6_ - Earthquakes And other Natural Hazards...

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1 Earthquakes And other Natural Hazards Earthquake on Monday Magnitude 5.6
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(possible) Earthquake precursors • Drop in ground water level • Increase in pore fluid pressure • Change in ground elevation • Lateral shifting of ground • Foreshocks • Increase in amount of radon gas To be useful, an earthquake predicition must include: • A date/time window • A well-defined geographic area • Probability estimate • Derived from a proven, tested method Seismic Wave Speed (P-waves) • In air: 330m/s • In water: 1450m/s • 5000-7000m/s in typical crust • >8000m/s in mantle and core • in granite: 5000m/s =18,000kph =11,200mph Seismic Wave Speed (S-waves) • 3000-4000m/s in typical crust • >4500m/s in mantle Seismic Wave Speed (Love waves) • 2000-4400m/s Seismic Wave Speed (Rayleigh waves) • 2000-4200m/s 4/28/2009 topic • Earthquake risks and prediction (part 2) outline • How does the Japan EQ early warning system work? • How prepared is the Bay area?
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EQ-lect9_6_ - Earthquakes And other Natural Hazards...

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