Lecture 22 (November 18)

Lecture 22 (November 18) - Still on site effects 1971 San...

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Still on site effects 1971 San Fernando Eq o Ground motions/accelerations were so high that the road flipped into the air People believed that the maximum horizontal acceleration of the ground was 0.3 g For something to get thrown into the air it, there must be vertical acceleration over 1.0 g (faster than the force of gravity) o Never buy a house on the hanging wall of a reverse fault Foreshock o (def.): Smaller magnitude event that precedes the main shock o Requirements Must be in approximately same location as main shock (within 1 fault length) Must be within same time period (seconds to months) o Problem Don’t know it’s a foreshock until and unless you have a subsequent larger main shock o History April 1992 Joshua Tree Eq M W 6.1 (classic foreshock) July 1992 Landers Eq M W 7.3 There is a 5% chance that any eq is a foreshock o some later, larger eq 95% of the time an earthquake is not a foreshock o Depth Eqs with shallow hypocenters usually have foreshocks
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This note was uploaded on 01/27/2009 for the course GEOL 240Lxg taught by Professor 12:30-01:50pm during the Fall '07 term at USC.

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Lecture 22 (November 18) - Still on site effects 1971 San...

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