Numerical modelling of seismoelectric wave fields stimulated by a ground surface source in layered porous media

Abstract:

_{In this work, we propose a new algorithm combining the Luco-Apsel-Chen generalized reflection and transmission method and the peak-trough averaging method to deal with the case of a ground surface source which leads to the slow convergence problem in seismoelectric modelling. The new algorithm is verified to be precise through comparison with analytical solutions. Besides, we verify the validity of the program code by reciprocity tests considering both source and receivers located on ground surface. Later, computational efficiency comparison is performed, it turns out the new algorithm can dramatically reduce the computational time when the source-receiver depth difference is much smaller than the seismic wavelength. Finally, seismoelectric couplings are investigated by adopting the proposed algorithm. Our numerical results show that the electric signals recorded by ground surface receivers exhibit a few milliseconds earlier than seismic signals due to the evanescent seismoelectric conversion. This is the first modelling result of explorational case capable of explaining similar phenomena reported in geophysical field observations on electrokinetic effect over a long history.}