GEOL 213 Lecture Notes - Lecture 9: Subduction, Elastic-Rebound Theory, Lithosphere
13 Nov 2020
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Document Summary
Earth"s internal heat transferred via convection to drive plate tectonics. 95% of earthquakes are associated with motions on or near plate boundaries. Spreading ridges & ocean/ocean subduction zones earthquakes cluster in very narrow zones. Characteristics of plate boundaries involving mainly oceanic lithosphere. Plate boundary in continental lithosphere deformation and earthquakes occur across broad area. Spreads seismic hazard out over a large region. Plate motion is directly measured by marking changes in location of points on the surface. Gps (global positioning system) satellite receivers are commonly used to track this motion. Near locked active faults, motion of crust is retarded and rocks are stretched and bent by plate motion. Eventually friction is overcome and rocks snap back along the fault; elastic rebound. Forces (stress) accumulating on faults can be estimated using gps and other measures of crustal deformation. Fault slip rates are used to make estimates of how often large earthquakes can be expected. Not all active faults have large earthquakes.
