Single station earthquake characterization for early warning

Andrew B. Lockman and Richard M. Allen
University of Wisconsin-Madison

Bull. Seismol. Soc. Am. 95 (6), 2029-2039, doi: 10.1785/0120040241, 2005.

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Abstract We use data from 50 earthquakes in southern California to test the accuracy of event parameter determination using single seismic stations for the purpose of early warning. Earthquake magnitude, hypocentral distance, and back azimuth are all estimated using P-wave arrivals only. There is a wide range in the accuracy of event parameters determined by different seismic stations. One quarter of the stations produce magnitude estimates with errors less than ±0.3 magnitude units, hypocentral distances within ±15km, and back azimuth calculations within ±20 degrees. This accuracy is more than sufficient to provide useful early warning. Using P-wave arrivals is the most rapid method of delivering earthquake early warning and may permit a few seconds notice of impending ground motion even in the epicentral region. Our results show that networks using a P-wave detection approach for early warning can increase the accuracy of their systems by using station-specific scaling relations between P-wave characteristics and earthquake source parameters and by identifying poor stations. Further, because individual stations are able to deliver an accurate early warning, the option of utilizing the technology in regions which lack a dense seismic network but are in need of seismic hazard mitigation becomes possible.