Calculating California seismicity rates

Open-File Report 2007-1437- I
Prepared in cooperation with the California Geological Survey and the Southern California Earthquake Center



Empirically the rate of earthquakes = magnitude M is well fit by the Gutenberg-Richter relationship, logN=a-bM (1) where N is the number of earthquakes = M over a given time period, a is the number of M = 0 earthquakes over the same period, and b is a parameter that determines the ratio of larger to smaller earthquakes (Ishimoto and Iida 1939; Gutenberg and Richter 1944). Thus to characterize the seismicity rate, N, and risk in a given region we need to solve for the values of a and b. Here we are concerned with solving for the long term average values of these parameters for the state of California. My primary data source is a catalog of 1850-2006 M = 4.0 seismicity compiled with Tianqing Cao (Appendix H). Because earthquakes outside of the state can influence California I consider both earthquakes within the state and within 100 km of the state border (Figure 1).

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Calculating California seismicity rates
Series title Open-File Report
Series number 2007-1437
Chapter I
DOI 10.3133/ofr20071437I
Edition Version 1.0
Year Published 2008
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Hazards Program, Earthquake Science Center
Description iii, 41 p.
Larger Work Type Report
Larger Work Subtype USGS Numbered Series
Larger Work Title Appendix I in The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)
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