HR: 16:15h
AN: G24A-02 INVITED    [Abstracts]
TI: The 28^th September 2004 Parkfield earthquake revisited through high-rate GPS data inversion.
AU: * Houlié, N
EM: houlie@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215, Mc Cone Hall - University of California, Berkeley, CA 94720, United States
AU: Dreger, D
EM: dreger@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215, Mc Cone Hall - University of California, Berkeley, CA 94720, United States
AU: Ahyi, K
EM: ahyi@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215, Mc Cone Hall - University of California, Berkeley, CA 94720, United States
AU: Romanowicz, B
EM: barbara@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215, Mc Cone Hall - University of California, Berkeley, CA 94720, United States
AB: Increasingly, Global Positioning System (GPS) data can also be used in real time to complement seismic data in providing robust real-time continuous earthquake information, and potentially, early warning. The occurrence of the Parkfield earthquake on the 28^th of September 2004 provides an opportunity to test the sensitivity and reactivity of network, data processing algorithms, and the implementation of GPS static and temporal solutions in finite-source inversions. Incorporation of GPS data in realtime processing algorithms is important for several reasons. First, static deformation with adequate station coverage can be used to independently determine the orientation and dimension of fault rupture, as well as the scalar seismic moment. This processing complements routine moment tensor (MT) processing, providing needed redundancy, but goes beyond the MT with the potential for causative fault plane identification and determination of fault rupture dimensions. The dimensions of the rupture plane derived from GPS data can then be used to improve ShakeMap by accounting for rupture finiteness. Second, the rapidly determined deformation may also be integrated into joint inversions with seismic waveform data for kinematic rupture models. This can be accomplished using static deformation estimates, as well as displacement time series derived from high-rate GPS data. Thirdly, GPS provides a strong motion displacement meter capability for the largest earthquakes. Double integration of acceleration to displacement to recover the broadband time series with static offset can be problematic, whereas GPS potentially can measure it directly. We first present the calibration of a GPS time series by comparing it with records from seismic sensors for the Parkfield event, validating the use of the GPS in the near-field during a large event. Finite-source inversion results based on static GPS, GPS time series, as well as combinations of these data with seismic records will be compared. The sensitivity of the inversion results to the distribution of the near-field GPS sites will be presented. Realtime implementation strategies at the Berkeley Seismological Laboratory will be discussed.
DE: 1294 Instruments and techniques
DE: 7203 Body waves
DE: 7209 Earthquake dynamics (1242)
DE: 7250 Transform faults
DE: 7255 Surface waves and free oscillations
SC: Geodesy [G]
MN: 2007 Fall Meeting