EPSC 201 Lecture Notes - Lecture 8: Thrust Fault, Hypocenter, Epicenter
4 Sep 2018
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Document Summary
Fault: when the strength of rock is exceeded and results in failure. Stress: applied to rocks to cause a fault. Strain: the deformation of rock caused by stress. Sudden movement along faults is the most common cause of earthquakes. Hypocenter: where fault slip occurs usually on a fault surface. Fault trace is the ground surface expression of a fault. Rock snaps back after slip along fault releases stress. Large earthquakes have larger slip areas displacement near hypocenter. Faults can offset rocks by 100s of km over time. S waves (rayleigh) shear body waves cause ground to undulate up and down. L waves (love) surface waves cause the ground to shimmy back and forth. Verticle-motion seismometer: detects up and down ground motion. Horizontal-motion seismometer: detects back and forth ground motion. P waves always arrive first, then the s waves. Waves are separated in time separation grows with distance from epicenter. Time delay used to establish distance can be graphed.
