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International Journal of Geophysics
Volume 2012, Article ID 543482, 8 pages
Research Article

Evaluating the RELM Test Results

1Department of Physics, University of California, Davis, Davis CA 95616, USA
2Graduate Institute of Geophysics, National Central University, Jhougli 320, Taiwan
3Department of Geology, University of California, Davis, Davis CA 95616, USA
4Theory Section, Santa Fe Institute, Santa Fe, NM 87501, USA

Received 15 July 2011; Revised 2 December 2011; Accepted 19 December 2011

Academic Editor: RodoÌfo Console

Copyright © 2012 Michael K. Sachs et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider implications of the Regional Earthquake Likelihood Models (RELM) test results with regard to earthquake forecasting. Prospective forecasts were solicited for earthquakes in California during the period 2006–2010. During this period 31 earthquakes occurred in the test region with . We consider five forecasts that were submitted for the test. We compare the forecasts utilizing forecast verification methodology developed in the atmospheric sciences, specifically for tornadoes. We utilize a “skill score” based on the forecast scores of occurrence of the test earthquakes. A perfect forecast would have , and a random (no skill) forecast would have . The best forecasts (largest value of ) for the 31 earthquakes had values of to . The best mean forecast for all earthquakes was . The best forecasts are about an order of magnitude better than random forecasts. We discuss the earthquakes, the forecasts, and alternative methods of evaluation of the performance of RELM forecasts. We also discuss the relative merits of alarm-based versus probability-based forecasts.