Gutenberg-Richter Frequency-Magnitude Distribution

The frequency-magnitude distribution follows the an equation developed by Gutenber and Richter of the form log(n) = A - bM.  The b-value is usually about 1. 

 Here are some yearly statistics on the number of earthquakes worldwide for 1987 - 1997, from the web site http://www.geo.lsa.umich.edu/~crlb/COURSES/117/Lec15/eqfreq.html

 Magnitude     1987   1988   1989   1990   1991   1992  1993  1994  1995  1996  1997

 8.0 to 8.9         0          0         1         0         0        0         1        2        3        1        0
 7.0 to 7.9       11          8         6       12       11      23       15      13      22      21      18
 6.0 to 6.9     112        93       79     115     105    104     141    161    185    160    124
 5.0 to 5.9   1437    1485   1444   1635   1469  1541   1449  1542  1327  1223  1099
 4.0 to 4.9   4146    4018   4090   4493   4372  5196   5034  4544  8140  8794  8522

 

 

Manitude Range

Average Number per Year
1987-1997

4.0-4.9

5577.182

5.0-5.9

1422.818

6.0-6.9

125.363

7.0-7.9

14.545

8.0-8.9

0.727

 

Below are two graphs of this data.  The first has a linear Y axis displaying the average number of earthquakes in each of the magnitude intervals per year.  In the second graph, the Y axis is logarithmic.  Along with the actual data values there is a second series of points with a slope of 1.0.  The deviation from a slope of one is quite small.  It is not surprising that the number of events in the 4.0 - 4.9 magnitude range is less than expected from a slope of one, because the global catalog is not complete for earthquakes that are this small.

Chart Frequency Magntiude Graph

Chart 1987-1997 Frequency Mangitude Distribution


Last Updated on 6/15/00

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