(General session) Mining and underground construction machineries / Rock Engineering / Resource based economy and social system / Mining technologies

[2409-17-07] [Student presentation: Master’s course]Source time function estimation using full-waveform inversion approach

○Xiaoqian Yu¹, Hitoshi Mikada¹, Junichi Takekawa¹, Shibo Xu¹ (1. Kyoto University)

Chairman:Akira Sato (Kumamoto University)

Keywords:source time function, full-waveform inversion, backpropagation

Earthquake source inversion is essential in earthquake physics and applied studies in earthquake engineering. Accurate source time functions can be estimated by the full-waveform inversion (FWI) approach through the backpropagation algorithm in a three-dimensional elastic case. The residual wavefield, i.e. the differences between observed and simulated wavefields, are back-propagated in time from the receiver to estimate the distribution of gradient of the L2-norm error function to minimize the total error in the backpropagated strain wavefield. On the basis of this method, an iterative process of the conjugate gradient method is conducted with the line search to find an optimum step length of an update vector in the parameter space. The results show that the prescribed source time function is well estimated, and the error function converges within several iteration steps. For the sources of high complexity, this approach can be applied to describe the detailed rapture process and the asperity of earthquakes.