HR: 10:30h
AN: G22A-01    [Abstracts]
TI: California Real Time Network: Test bed for earthquake early warning systems
AU: * Crowell, B W
EM: bwcrowel@ucsd.edu
AF: Scripps Institution of Oceanography, IGPP 0225 9500 Gilman Drive, La Jolla, CA 92093-0225, United States
AU: Bock, Y
EM: ybock@ucsd.edu
AF: Scripps Institution of Oceanography, IGPP 0225 9500 Gilman Drive, La Jolla, CA 92093-0225, United States
AU: Squibb, M
EM: msquibb@ucsd.edu
AF: Scripps Institution of Oceanography, IGPP 0225 9500 Gilman Drive, La Jolla, CA 92093-0225, United States
AB: More than 80 CGPS stations in southern California have been upgraded to a 1 Hz sample rate, including stations from the SCIGN and PBO networks. The upgraded stations comprise the California Real Time Network and provide continuous 1 Hz (upgradable to 10-20 Hz at some stations) GPS displacement waveforms and troposphere delay estimates with a latency of less than 1 s. With funding from NASA, CRTN provides a test bed for developing advanced in situ-based observation systems within a modern data portal environment, which can be extended seamlessly to the entire PBO region and to other plate boundaries. We describe a prototype early warning system for earthquakes using CRTN, which is also being deployed at other plate boundaries. We demonstrate the elements of an earthquake early warning system by analyzing the 2003 Mw 8.3 Tokachi-Oki thrust earthquake off Hokkaido Island detected by the dense Japan national real-time CGPS network. The network has an approximately 20-km spacing with 1156 stations streaming 1 Hz data to a central facility. A Delaunay triangulation of the network is created every second and the 1 Hz displacements within triangular element are converted to principal components of strain to detect the event. The large spatial extent allows us to compute displacement waveforms relative to a station well away from the affected region through a real-time network adjustment algorithm. We then compute the earthquake hypocenter through a grid search and L2-norm minimization. The final earthquake source model is computed using the total displacement waveforms, the earthquake hypocenter and the predetermined fault structure in the inversion program Defnode. We finish by showing the method in action for the November, 2008 ShakeOut earthquake scenario using CRTN. We show that more accurate earthquake source parameters can be obtained by utilizing higher rate GPS up to 10-20 Hz.
UR: http://sopac.ucsd.edu/projects/realtime/
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 1294 Instruments and techniques
DE: 7209 Earthquake dynamics (1242)
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Geodesy [G]
MN: 2009 Joint Assembly