HR: 1340h
AN: S23A-0301    [Abstracts]
TI: The False-Alarm Rate of Accelerating Moment Release, and its Relationship to Probabilistic Earthquake Rupture Forecasts.
AU: * Levin, S Z
EM: slevin@fullerton.edu
AF: California State University, Fullerton, Department of Geological Sciences P.O. Box 6850, Fullerton, CA 92834-6850 United States
AU: Ikeda, N
EM: nikeda@qwickconnect.net
AF: California State University, Fullerton, Department of Geological Sciences P.O. Box 6850, Fullerton, CA 92834-6850 United States
AU: Reissman, J
EM: jeff@rxperts.net
AF: California State University, Fullerton, Department of Geological Sciences P.O. Box 6850, Fullerton, CA 92834-6850 United States
AU: Bowman, D D
EM: dbowman@fullerton.edu
AF: California State University, Fullerton, Department of Geological Sciences P.O. Box 6850, Fullerton, CA 92834-6850 United States
AB: It has been suggested that large earthquakes are preceded by a systematic increase in the rate of background seismicity in a broad region around the impending event. This rate change, known as "accelerating moment release" (AMR), has been proposed as a precursory signal that could be used to forecast large earthquakes. In this approach, the observation of accelerating seismicity would represent a period of increased likelihood of a large earthquake, termed an "alarm". However, as with any pattern-recognition scheme there is a finite probability that the observed rate changes could be due to random variations in background seismicity rate. An observation of accelerating moment release that does not culminate in a large earthquake is called a "false-alarm". To test the probability of accelerating moment release arising from random fluctuations in the seismicity rate, synthetic earthquake catalogs are generated and searched for AMR. The frequency of accelerating moment release in these randomly generated catalogs represents the false-alarm rate of the AMR forecasting methodology. The importance of aftershocks and the spatial distribution of seismicity on discrete faults is also explored by introducing random clustering in the synthetic catalogs. The false-alarm rate is shown to depend strongly on the degree of acceleration in the background seismicity. Assuming that the false-alarm rate is the probability that the observed acceleration is occurring randomly, then the complement of the probability represents the likelihood that the observation is a precursor to an earthquake. This allows time-dependent probabilistic rupture forecasts to be made based on observations of accelerating moment release.
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2004 AGU Fall Meeting