SEMINAR - David Bowman

Accelerating Moment Release Before Large Earthquakes: Life and Death of an Earthquake Prediction Scheme

David Bowman
Department of Geological Sciences
California State University, Fullerton

Postponed

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. Bowman and King [GRL, 2001] demonstrate that the pre-mainshock stress field, as indicated by a simple backslip model of the event, can be used to define the critical region that optimizes the precursory AMR signal. The observation of accelerating seismicity within this region represents a period of increased likelihood of a large earthquake. With sufficient knowledge of the regional tectonics, it should be possible to estimate the likelihood of earthquake rupture scenarios by searching for AMR related to stress accumulation on specific faults. This talk will present two algorithms that randomly search global plate boundaries for AMR signals before potential large events. Each plate boundary is searched for AMR using circular regions following the method of Bowman et al.[1998] and fault-based stress accumulation regions following the approach of Bowman and King [2001]. The fault-based algorithm uses a schematic model of the plate-boundary faults to represent potential sources; subduction zones are modeled as single mega-thrust faults, spreading centers as a normal faults, and transforms as single strike-slip faults. In each approach, the entire global plate boundary network is populated by potential sources and searched for precursory AMR. False-alarm and Failure-to-predict statistics are calculated based on historical seismicity; given the heterogeneity of modern instrumental catalogs, these statistics suggest that the current AMR algorithm does not provide significant predictive power.