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Unformatted text preview: GEOL 0820 Ramsey Natural Disasters Spring, 2011 LECTURE #7: Earthquake Disasters: Monitoring & Mitigation Date: 1 February 2011 I. In the News … • volcanic eruption in Japan • notes … II. Introduction • what are earthquakes (EQ’s)? o ground movement caused by the release of seismic energy o seismic energy is usually caused by the brittle failure of rocks under stress • important hazards to understand: o kills the most people per year (> 1 million/past century) o commonly strikes without precursors o 1000's of large EQ's every year ¡ ~ 20 are > M7.0 ¡ account for 90% of the energy released ¡ 80% of all the fatalities o recall: most of the fastest growing cities lie on the Pacific Rim and are threatened by large EQ's III. Earthquakes & Faults • what is an EQ? o sudden release of stored energy as the result of rapid movement between two blocks (plates) o energy stored because of plate movement and friction ¡ release point is the focus or hypocenter ¡ energy radiates out in all directions ¡ point on the surface directly above the focus is the epicenter ¡ fault trace: line where the fault/fracture intersects the surface Page 1/5 Earthquakes in CA/NV during one week • fault terminology: o headwall: rock layers above the fault plane o footwall: rock layers below the fault plane o fault types: ¡ normal (extensional) ¾ due to tensional forces; generally the smallest EQ’s ¾ hanging wall moves down with respect to the footwall...
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- Spring '08
- Plate Tectonics, EQ, large eq, Andreanof Islands