(General session) Rock Engineering / Mining technologies

[2K0101-07-06] [Student presentation: Master’s course] Finite fault source estimation using full-waveform inversion approach

○Xiaoqian Yu¹, Hitoshi Mikada¹, Junichi Takekawa¹ (1. Kyoto University)

Chairperson : Akihiro Hamanaka (Kyushu University)

Keywords:finite fault system, full-waveform inversion, backpropagation

Earthquake source and rapture process estimation have always been key issues in the geoscience world. To describe the source rapture of high complexity, it is necessary to utilize more information from the observed waveform data and develop the advanced inversion algorithm. Thus, the full-waveform inversion method and backpropagation technique are implemented in this study. We extract the full waveforms from the observed data, propagate the waveforms backward in time from receivers to the source region, and calculate the gradient of the misfit function based on the backpropagated strain wavefield. In this way, the optimization workflow using the conjugate gradient method can be utilized to minimize the L2-norm error function, which describes the misfit between the observed and synthetic waveform. Besides, to quantitatively estimate the kinematical characteristic of the earthquake source, the segmented finite fault system is used to represent the source of the earthquake. We determine the hypocenter first, and there are two nodal planes orthogonal to each other crossing at this point due to the symmetry of the focal mechanism. The method we illustrate above can be used to do the segmented analysis and determine which plane is the fault. We also build the finite fault model to estimate the details of the rapture process. This approach can be applied to image earthquakes of high complexity and reveal more detail about the asperity of earthquakes.