EARTHSC 1G03 Lecture 7: 1GO3 lecture 7 earthquakes F13.pdf
29 Oct 2014
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Document Summary
Civilization exists by geological consent, subject to change without notice. Earthquakes are shock waves or, in other words, vibrations within the earth. They are triggered by the sudden slippage of rock along fault planes in the crust or mantle. The deformation that an object undergoes in response to stress (= force per unit area) is called strain. Local stress is usually caused by regional shear stress, tensional stress, or compression stress in the crust. Strain energy accumulates at rough" spots on the plates. Foreshocks - small, early quakes as rocks begin to fracture. Aftershocks - rocks along fault adjust and transfer strain. The energy released during earthquakes pulverizes rocks, generates heat, and causes vibrations = seismic waves. The seismic waves originate in the earthquake focus, directly beneath the epicenter. Travel near the surface of the earth. Rock vibration parallel to transport direction (series of expansions/compressions) Slower than p waves (= shear waves)
