HR: 0800h
AN: S51B-0498    [Abstracts]
TI: Southern California Adjoint Source Inversions
AU: * Tromp, J
EM: jtromp@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91106, United States
AU: Kim, Y
EM: ykim@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91106, United States
AB: Southern California Centroid-Moment Tensor (CMT) solutions with 9 components (6 moment tensor elements, latitude, longitude, and depth) are sought to minimize a misfit function computed from waveform differences. The gradient of a misfit function is obtained based upon two numerical simulations for each earthquake: one forward calculation for the southern California model, and an adjoint calculation that uses time-reversed signals at the receivers. Conjugate gradient and square-root variable metric methods are used to iteratively improve the earthquake source model while reducing the misfit function. The square-root variable metric algorithm has the advantage of providing a direct approximation to the posterior covariance operator. We test the inversion procedure by perturbing each component of the CMT solution, and see how the algorithm converges. Finally, we demonstrate full inversion capabilities using data for real Southern California earthquakes.
DE: 7205 Continental crust (1219)
DE: 7215 Earthquake source observations (1240)
DE: 7290 Computational seismology
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting