Rapid Source Parameter Estimations of Southern California Earthquakes Using PreSEIS

Abstract

Earthquake early warning (EEW) systems provide real-time estimates of earthquake source and ground motion parameters to users before strong ground shaking occurs at sites of interest (Kanamori et al. 1997; Kanamori 2005). They make use of the fact that the most destructive ground shaking during an earthquake is caused by S- and surface waves, which travel much slower than P waves and also slower than electromagnetic signals carrying warnings to potential users. Real-time information systems can minimize loss of life and property damage and are therefore an important tool in short-term seismic hazard mitigation and disaster management (Wenzel et al. 2001). If an alarm can be issued seconds before the onset of the strong ground motions, automatic emergency actions can be initiated such as slowing down high speed trains or shutting down computers or gas distribution, for instance (Goltz 2002). EEW systems are of two main types, regional and on-site. The former uses a dense network of seismic stations to locate the earthquake, determine its magnitude, and estimate the ground motion at given sites of interest. The latter uses the observations at a single sensor to estimate the ensuing ground motion at the same site (Kanamori 2005). While regional systems work more accurately, they need more time to estimate earthquake source parameters.