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"
Abstract:
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.