GEOL 106 Lecture Notes - Lecture 5: Oceanic Crust, Plate Tectonics, Logarithmic Scale
23 Mar 2018
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Sensitive instruments around the world record the event (called seismographs) Focus and epicenter: epicenter- on the surface directly above the focus. Faults are fractures in bedrock along which movement has occurred. Fault rupture and propagation: most faults are locked except for brief, abrupt movements, faults do not slip all at once. Initial slip begins at focus and propagates along the fault surface. Strike-slip fault: horizontal motion: dip-slip fault: sub-vertical or vertical movement, normal dip-slip fault: down the rap, reserve dip-slip fault: up the ramp. Faults have a rock mass on either side of the discontinuity (break). Includes aftershocks: few minutes to a year after. Three types of plate boundaries: diverging, converging, transform. Strain can accumulate then suddenly release: plates move past each other horizontally, can result in large earthquakes, most californian earthquakes. San andreas fault movement, 2-5 cm per year. Subduction zone: reverse dip-slip faults, movement can be 10 cm or more per year.
