HR: 13:40h
AN: G23A-01 INVITED    [Abstracts]
TI: Integrating GPS and Seismic Data in Earthquake Source Inversions
AU: * Custodio, S
EM: susana@crustal.ucsb.edu
AF: University of California at Santa Barbara, Institute for Crustal Studies, Girvetz Hall, University of California at Santa Barbara, Santa Barbara, CA 93106-1100, United States
AU: Page, M T
EM: pagem@physics.ucsb.edu
AF: United States Geological Survey, 525 South Wilson Ave., Pasadena, CA 91106-3212, United States
AU: Archuleta, R J
EM: ralph@crustal.ucsb.edu
AF: University of California at Santa Barbara, Institute for Crustal Studies, Girvetz Hall, University of California at Santa Barbara, Santa Barbara, CA 93106-1100, United States
AB: Earthquake source inversions make use of recorded ground motion to image the seismic rupture. In general, two different types of data are used for this purpose: 1) records of the static field and 2) records of seismic waves. The static field data record the difference in ground positions before and after the earthquake; it can be used to infer the cumulative slip that occurs during an earthquake. However, it tells nothing about the temporal evolution of slip on the fault. In order to image the full space-time evolution of slip on the fault one must utilize data that record the radiated wavefield. The wavefield is normally captured by seismographs. High-rate GPS sensors also can record the radiated wavefield. However, these high-rate (1-Hz) GPS measurements are useful as seismograms in seismic source inversions only in a very limited frequency band. On the other hand, high-rate GPS can be very useful in seismic source inversions as it allows the determination of the truly co-seismic static field. In other words, the static field inferred from high-rate GPS does not include significant post-seismic deformation. Thus, the truly co-seismic static field provided by high-rate GPS data can be inverted to determine the cumulative slip that took place during the earthquake. In turn, the resulting cumulative slip distribution can then be used to constrain an inversion of the radiated wavefield for the temporal slip. Given the strong trade-offs between temporal and spatial parameters in inversions of the wavefield, it is extremely valuable to use a priori knowledge (in this case the cumulative slip). Accordingly, we developed a two-step procedure to combine GPS and seismic data in earthquake source inversions. In the first step we use the truly co-seismic static field (inferred from high-rate GPS) to infer the spatial distribution of cumulative slip on the fault. This inversion is performed on an irregular grid that takes into account the spatially heterogeneous resolving power of the GPS data. In the second step, we use records of ground acceleration to infer the space-time history of slip on the fault, while constraining the final slip distribution to match that inferred from the static field. This approach explores the resolving ability of each dataset (static and dynamic), thus using each dataset to determine appropriate parameters and leaving out unwanted artifacts.
DE: 0545 Modeling (4255)
DE: 1200 GEODESY AND GRAVITY
DE: 3260 Inverse theory
DE: 7200 SEISMOLOGY
DE: 7215 Earthquake source observations (1240)
SC: Geodesy [G]
MN: 2007 Fall Meeting