Passive Source Reverse Time Migration Method to Image Discontinuity Beneath Irregular Free-surface

LIANG Zuokui, GE Zengxi

ACTA Scientiarum Naturalium Universitatis Pekinensis - - Contents -

Deparment of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871; † Corresponding author, E-mail: zge@pku.edu.cn

Abstract Because the most used finite difference method to calculate wave propagation cannot handle irregular boundaries easily, a hybrid boundary element and finite difference method is proposed. Firstly, the boundary element method is used to obtain the wavefileds along a horizontal boundary which is going to be the boundary condition of the finite difference method in the next stop. Then the finite difference method is applied to obtain the wavefields under the interface. The wavefields are separated to vector P-wave and S-wave constituents, and considering the coherence of P-wave and S-wave in a conversion point, the image condition of cross-correlation between P- and S-waves is applied to obtain discontinuity image underground. Synthetic tests show the effectiveness of the proposed method. Key words irregular free-surface; boundary element method; finite difference method; passive source; reverse time migration

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