earthquakes 4

earthquakes 4 - why do earthquakes occur? what is an...

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why do earthquakes occur? what is an earthquake? sudden movement of blocks of rocks on either side of a fault (crack that  has experienced slip). movement must be fast enough to generate seismic waves. earthquakes occur on faults. what causes this movement? simple answer is stress.  what is stress? how does it cause earthquakes force = mass x acceleration of gravity (g)  stress = force divided by the area over which the force is acting. the force that polar bear  is exerting on the ice is the same force it applies while lying on the ice. but the stress is different.  less stress when lying down. stress is why things break.  stress (abbreviated with sigma) acts in 3 dimensions. (like when you are on the  bottom of a pool. you feel water pressure from every angle)  1.isotropic stress = stress from all angles. 2.tectonic stress: not the same pressure in all directions.ultimately related  to relative plate motions geologic stress is always compressional (always pushing in) due to rocks above you. normal stress (perpendicular-to stress)
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earthquakes 4 - why do earthquakes occur? what is an...

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