Lecture 19 Mar 14 2008 Earthquakes

Lecture 19 Mar 14 2008 Earthquakes - Magnitude 7.9 quake....

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Unformatted text preview: Magnitude 7.9 quake. Mexico City, 1985. 9,500 died. The relative movement of the plates at their boundaries results in deformation of solid rock. When rock being deformed suddenly breaks along a fault, the two blocks of rock on both sides of the fault slip suddenly. The resulting shaking or vibration of the ground is an earthquake. While the rock is bending without breaking, it is behaving elastically (ductile deformation). Eventually the strain is so great that the rock ruptures (brittle deformation), the rocks rebound. The distance of displacement is the slip. The time from step (a) to (d) may be tens to thousands of years. We can see the slip along this transform fault in California. The point at which the slip initiates is the focus of the earthquake. Seismic waves radiate outward in all directions from the focus. The point on the surface directly over the focus is the epicenter. This fault scarp is an abrupt, steep slope separating two relatively level areas. Fault scarps form only where the fault reaches all the way to Earth’s surface. Deep-focus earthquakes coincide with convergent boundaries. Typically, the earthquakes occur along the inclined plane of the subducted plate.inclined plane of the subducted plate....
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This note was uploaded on 04/11/2008 for the course EVSC 280 taught by Professor Herman during the Spring '08 term at UVA.

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Lecture 19 Mar 14 2008 Earthquakes - Magnitude 7.9 quake....

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