Lecture 14

# Lecture 14 - Omoris Law for Aftershocks N= A (t + C ) p N =...

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Omori’s Law for Aftershocks N = A t + C ( ) p N = Rate of aftershocks (Number per day or Number per hour) t = time since mainshock A, C, and p are constants. ( p near 1)

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Gutenberg-Richter Magnitude-Frequency Relation N M = 10 a bM N = Number of magnitude M earthquakes in a given region in a given time interval a = constant telling how active the region is. There are 10 a M=0 earthquakes in the region during the time interval. b = constant telling how the relative number of earthquakes depends on their size (b is usually 1). N M 1 N M = 10 a 10 b ( M 1) 10 a 10 b ( M ) = 10 b ( M 1 M ) = 10 b

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Each time the magnitude is reduced by one unit, there are 10 times as many earthquakes . For each magnitude 7 earthquake there are: 10 M=6 100 M=5 1000 M=4 Etc.
Energy-Magnitude Relation E M =10 11.8 + 1.5 M ergs = Energy of a magnitude M earthquake E M + 1 E M = 10 11.8 + 1.5( M + 1) 10 11.8 + 1.5 M = 10 11.8 ( ) 10 1.5( M + 1) ( ) 10 11.8 ( ) 10 1.5 M ( ) = 10 1.5( M + 1) 1.5 M = 10 1.5 30

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For each unit increase in magnitude, there is a factor of
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## This note was uploaded on 01/11/2010 for the course GEOL 240Lxg at USC.

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Lecture 14 - Omoris Law for Aftershocks N= A (t + C ) p N =...

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