S33B-2765
Prototype Earthquake Early Warning System for Areas of Highest Seismic Risk in the Western U.S.
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Yehuda Bock1, Jianghui Geng1, Dara Goldberg2, Jessie K Saunders2, Jennifer Susan Haase2, Melinda B Squibb2, Diego Melgar3, Brendan W Crowell4, Robert W Clayton5, Ellen Yu5, Christian P Walls6, Doerte Mann6, David Mencin7 and Glen S Mattioli7, (1)University of California San Diego, La Jolla, CA, United States, (2)Scripps Institution of Oceanography, La Jolla, CA, United States, (3)University of California Berkeley, Berkeley, CA, United States, (4)University of Washington, Seattle, WA, United States, (5)California Institute of Technology, Pasadena, CA, United States, (6)UNAVCO, Inc. San Clemente, San Clemente, CA, United States, (7)UNAVCO, Inc. Boulder, Boulder, CO, United States
Abstract:
We report on a prototype earthquake early warning system for the Western U.S. based on GNSS (GPS+GLONASS) observations, and where available collocated GNSS and accelerometer data (seismogeodesy). We estimate with latency of 2-3 seconds GNSS displacement waveforms from more than 120 stations, focusing on the southern segment of the San Andreas fault, the Hayward and Rodgers Creek faults and Cascadia. The displacements are estimated using precise point positioning with ambiguity resolution (PPP-AR), which provides for efficient processing of hundreds of “clients” within the region of interest with respect to a reference frame well outside the expected zone of deformation. The GNSS displacements are useful for alleviating magnitude saturation concerns, rapid earthquake magnitude estimation using peak ground displacements, CMT solutions and finite fault slip models. However, GNSS alone is insufficient for strict earthquake early warning (i.e., P wave detection). Therefore, we employ a self-contained seismogeodetic technique, where collocations of GNSS and accelerometer instruments are available, to estimate real-time displacement and velocity waveforms using PPP-AR with accelerometers (PPP-ARA). Using the velocity waveforms we can detect the P wave arrival for earthquakes of interest (>M 5.5), estimate a hypocenter, S wave propagation, and earthquake magnitude using Pd scaling relationships within seconds. Currently we are gearing up to receive observatory-grade accelerometer data from the CISN. We have deployed 25 inexpensive MEMS accelerometers at existing GNSS stations. The SIO Geodetic Modules that control the flow of the GNSS and accelerometer data are being upgraded with in situ PPP-ARA and P wave picking. In situ processing allows us to use the data at the highest sampling rate of the GNSS receiver (10 Hz or higher), in combination with the 100 Hz accelerometer data. Adding the GLONASS data allows for increased precision in the vertical, an important factor in P wave detection, and by reducing outliers, increasing the number of visible satellites and significantly reducing the time required for reinitialization of phase ambiguities. We plan to make our displacement and velocity waveforms available to the USGS ShakeAlert system and others in Earthworm format.
