Earthquakes Effects of Earthquakes Earthquakes produce several types of effects, all of which can cause loss of property and human life Ground Motion is the familiar trembling and shaking of the land during an earthquake Fire is a problem just after earthquakes because of broken gas and water mains and fallen electrical wires Landslides can be triggered by ground shaking, particularly in larger quakes Liquefaction occurs when water-saturated soil or sediment sloshes like a liquid during a quake Permanent displacement of the land surface can also occur, leaving fractures and scarps Tsunami Very large sea waves, caused by sudden upward or downward movement of the sea floor during submarine earthquakes, are known as Tsunami (seismic sea waves) Tsunami are generally produced by magnitude 8+ earthquakes (?great? earthquakes) May also be generated by large undersea landslides or volcanic explosions Travel across open ocean at speeds of >700 km/hr Reach great heights in coastal areas with gently sloping seafloor and funnel-shaped bays They may be almost imperceptible in deep water. Low wave height (amplitude). Long wave length (frequency). As water shallows, waves slow from fractional drag. Waves grow in height, reaching 10-15 m or more. Tsunami destruction of the coast depends upon? Offshore bathymetry. Broad shallows increase amplitude but sap wave energy. Quick deep-to-shallow transition ? Deadliest condition. Waves have maximum energy. Wave heights are modest. Water pours onto land as a sheet. Topography of shore. Broad, low land ? Maximum damage. Steep rise of land ?less damage. Earthquake Locations Generally occur in linear belts Intraplate earthquakes also occur and quite severe Linear belts correspond to plate boundaries most earthquakes occur at plate boundaries Earthquakes occur at each of the three types of plate boundaries: divergent, transform, and convergent Earthquake focal depths are Deep Intermediate Shallow Most important concentrations are in the circum-Pacific and Mediterranean-Himalayan belts
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