GS1004 Spotila 19 September, 2016 Lecture 9: Consequences of Tectonics: Earthquakes I Relevant reading: Chp. 8, p. 244-279. Motivating questions: What are earthquakes? Why do we have earthquakes, and where do they occur? Can earthquakes be predicted? What controls the hazards of earthquakes? Earthquakes are produced by sliding of crust along active faults. The motion is produced by plate tectonics. Thus... most earthquakes occur among plate boundaries. Although rare events occur within plates, away from boundaries. e.g. 1886, M6.7; Charleston, SC; 1812, M8.2; New Madrid, MO. Why? Same forces transmitted throughout the plate, just much lower rate. Faults produce earthquakes (not the other way around) in the upper crust (<15 km depth). An earthquake is radiation of energy due to friction on the fault as the fault moves. What is the geometry of earthquakes? Small earthquakes are approximated as points, but big earthquakes occur... Along fault planes; they can be hundreds of miles long.
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- Spring '08