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| | Abstract | | We propose a passive seismic reflection imaging method without source information based on reverse time migration (RTM) for exploring deep crustal structures using earthquakes. In the proposed RTM method using multiple reflections between surface and subsurface boundaries, we correlate forward- and backward-extrapolated wavefields of the same observation records from all receivers at once. We implemented acoustic RTM with a scalar wave equation and elastic RTM with a velocity-stress formulation for wavefield modelling. Separate P- and S-wave reflection images can be obtained by adopting scalar and vector potential formulations in elastic RTM. In this study, we present two-dimensional numerical simulations with a regional crustal model of southwest Japan. We show the validity of the proposed method using idealized dense observations and possible difficulties in realistic observation. By applying elastic RTM, the degradation problem with artefacts due to the elastic wave effect in acoustic RTM can be overcome, and the resolution of reflection images can be improved by the shorter wave length of S-wave than that of P-wave. |
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