Earthquake Hazards Program

U.S. Geological Survey
Open-File Report 2007-1162
version 2.0

Earthquake Rate Model 2 of the 2007 Working Group for California Earthquake Probabilities, Appendix D: Magnitude-Area Relationships

By Ross S. Stein

2007

two x-y graphs
Two models that currently receive equal weight in Earthquake Rupture Model 2.2 (from figure 6).

Summary

The Working Group for California Earthquake Probabilities must transform fault lengths and their slip rates into earthquake moment-magnitudes. First, the down-dip coseismic fault dimension, W, must be inferred. We have chosen the Nazareth and Hauksson (2004) method, which uses the depth above which 99% of the background seismicity occurs to assign W. The product of the observed or inferred fault length, L, with the down-dip dimension, W, gives the fault area, A. We must then use a scaling relation to relate A to moment-magnitude, Mw. We assigned equal weight to the Ellsworth B (Working Group on California Earthquake Probabilities, 2003) and Hanks and Bakun (2007) equations. The former uses a single logarithmic relation fitted to the M?6.5 portion of data of Wells and Coppersmith (1994); the latter uses a bilinear relation with a slope change at M=6.65 (A=537 km2) and also was tested against a greatly expanded dataset for large continental transform earthquakes. We also present an alternative power law relation, which fits the newly expanded Hanks and Bakun (2007) data best, and captures the change in slope that Hanks and Bakun attribute to a transtion from area- to length-scaling of earthquake slip. We have not opted to use the alternative relation for the current model. The selections and weights were developed by unanimous consensus of the Executive Committee of the Working Group, following an open meeting of scientists, a solicitation of outside opinions from additional scientists, and presentation of our approach to the Scientific Review Panel. The magnitude-area relations and their assigned weights are unchanged from that used in Working Group (2003).


Download this report as a 16-page PDF file (of2007-1162v2.pdf; 2.3 MB).

For questions about this report, contact Ross Stein.

Suggested citation and version history


Download a free copy of the current version of Adobe Reader.

| Help | PDF help | Publications main page | Western Open-File Reports for 2007 |
| Geology | Earthquake Hazards Program |


This report is available only on the Web


Accessibility FOIA Privacy Policies and Notices

Take Pride in America home page. USA.gov logo U.S. Department of the Interior | U.S. Geological Survey

URL: http://pubs.usgs.gov/of/2007/1162/
Page Contact Information: Michael Diggles
Page Last Modified: November 19, 2007 (mfd)