Date & Time: 17:00 to 18:30, 25 February, 2002
Place: Room No. D570, Disaster Prevention Research Institute(DPRI)
Speaker: Prof. Xiaofei Chen, Department of Geophysics, Peking University, China
Title: "A hybrid inversion algorithm for retrieving earthquake source rupture process"
A new hybrid inversion method for simultaneously retrieving the slip vectors and time history of the rupture process of a finite earthquake fault from near-field strong motion data has been developed based on the newest development in the nonlinear optimization study. Generally speaking, the simultaneously inversion of slip vectors and rupture times of an earthquake fault is a nonlinear inversion problem. To efficiently solve such problem, we first separated this nonlinear inversion problem into two sub-problems: a linear inversion problem with respect to the slip vectors, and a nonlinear inversion problem with respect to the rupture times; then alternately solve these two sub-problems in each iterative loop. Secondly, we incorporated the trust region BFGS updating scheme, the newest development of nonlinear optimization study, to solve the nonlinear inversion sub-problem effectively. Finally, to assess the validity and applicability of this new hybrid inversion algorithm, we designed three typical earthquake source models, i.e., non-uniform Haskell dislocation model, non-uniform crack model and complex asperity model, as test examples. Taking the synthetic seismograms as waveform data, we applied our new hybrid inversion algorithm on these synthetic data for inverting these designed earthquake source process. The test results indicated that this new inversion algorithm provides an effective tool for retrieving the earthquake source process from the near-field strong motion waveform data.