GEOL 1010 Lecture Notes - Lecture 11: San Andreas Fault, Mercalli Intensity Scale, Shear Modulus
28 Oct 2016
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Document Summary
Another fault definition: strike-slip fault: left lateral [sinistral] and right lateral [dectral]. Earthquake size: described by two measurements. Amount of ground motion (magnitude: mercalli intensity scale -- amount of shaking damage. Roman numerals assigned to different levels of damage. Damage diminishes intensity with distance: magnitude. Log of the maximum amplitude of ground motion. Measured by seismometer at a specific distance. Richter scale -- original, useful near the epicenter. Moment magnitude scale -- more accurate measure. M7. 0 is a thousand times an m4. 0. The smallest a person can feel is about a 2. 5. Moment magnitude: shear modulus of the fault, shear stress to shear strain. How much you push it to how much it moves. mda: energy released can be calculated. M6. 0 -- the energy or the hiroshima atomic bomb. An increase of m1. 0 is a 32x increase in energy. It is possible to have a negative magnitude earthquake, but people won"t feel it.
