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A New Trigger Criterion for Improved Real-Time Performance of Onsite Earthquake Early Warning in Southern California

Seismological Laboratory, California Institute of Technology, 1200 E. California Boulevard, Mail Code 252-21, Pasadena, California 91125 mboese{at}gps.caltech.edu hauksson{at}gps.caltech.edu solanki{at}gps.caltech.edu hiroo{at}gps.caltech.edu

Y.-M. Wu

Department of Geosciences, National Taiwan University, Taipei, Taiwan drymwu{at}ntu.edu.tw

T. H. Heaton

Seismological Laboratory, California Institute of Technology, 1200 E. California Bldv., Mail Code 252-21, Pasadena, California 91125 heaton{at}gps.caltech.edu

We have implemented and tested an algorithm for onsite earthquake early warning (EEW) in California using the infrastructure of the Southern California Seismic Network (SCSN). The algorithm relies on two parameters derived from the initial 3 sec of P waveform data at a single seismic sensor: period parameter _c and high-pass filtered displacement amplitude P_d. Previous studies have determined empirical relationships between _c and the moment magnitude M_w of an earthquake, and between P_d and the peak ground velocity (PGV) at the site of observation. In 2007, seven local earthquakes in southern California with 4.0M_L4.7 have triggered the calculation of M_w and PGV by the EEW algorithm. While the mean values of estimated parameters were in the expected range, the scatter was large, in particular for the smallest events. During the same time period the EEW algorithm produced a large number of false triggers due to low trigger thresholds. To improve the real-time performance of the onsite approach, we have developed a new trigger criterion that is based on combinations of observed _c and P_d values. This new criterion removes 97% of previous false triggers and leads to a significant reduction of the scatter in magnitude estimates for small earthquakes.

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				R. M. Allen, P. Gasparini, O. Kamigaichi, and M. Bose The Status of Earthquake Early Warning around the World: An Introductory Overview Seismological Research Letters, September 1, 2009; 80(5): 682 - 693. [Full Text] [PDF]