A-priori rupture models for Northern California Type-A faults

Open-File Report 2007-1437- K
Prepared in cooperation with the California Geological Survey and the Southern California Earthquake Center
By: , and 

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Abstract

This appendix describes how a-priori rupture models were developed for the northern California Type-A faults. As described in the main body of this report, and in Appendix G, “a-priori” models represent an initial estimate of the rate of single and multi-segment surface ruptures on each fault. Whether or not a given model is moment balanced (i.e., satisfies section slip-rate data) depends on assumptions made regarding the average slip on each segment in each rupture (which in turn depends on the chosen magnitude-area relationship). Therefore, for a given set of assumptions, or branch on the logic tree, the methodology of the present Working Group (WGCEP-2007) is to find a final model that is as close as possible to the a-priori model, in the least squares sense, but that also satisfies slip rate and perhaps other data. This is analogous the WGCEP- 2002 approach of effectively voting on the relative rate of each possible rupture, and then finding the closest moment-balance model (under a more limiting set of assumptions than adopted by the present WGCEP, as described in detail in Appendix G). The 2002 Working Group Report (WCCEP, 2003, referred to here as WGCEP-2002), created segmented earthquake rupture forecast models for all faults in the region, including some that had been designated as Type B faults in the NSHMP, 1996, and one that had not previously been considered. The 2002 National Seismic Hazard Maps used the values from WGCEP-2002 for all the faults in the region, essentially treating all the listed faults as Type A faults. As discussed in Appendix A, the current WGCEP found that there are a number of faults with little or no data on slip-per-event, or dates of previous earthquakes. As a result, the WGCEP recommends that faults with minimal available earthquake recurrence data: the Greenville, Mount Diablo, San Gregorio, Monte Vista-Shannon and Concord-Green Valley be modeled as Type B faults to be consistent with similarly poorly-known faults statewide. As a result, the modified segmented models discussed here only concern the San Andreas, Hayward-Rodgers Creek, and Calaveras faults.

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title A-priori rupture models for Northern California Type-A faults
Series title Open-File Report
Series number 2007-1437
Chapter K
DOI 10.3133/ofr20071437K
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, Geologic Hazards Science Center
Description iii, 7 p.
Larger Work Type Report
Larger Work Subtype USGS Numbered Series
Larger Work Title Appendix K in The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2)
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