Finite-difference method for irregular surface boundaries in coupled seismic and electromagnetic waves simulation in porous media

All the studies about the coupled seismic and electromagnetic waves in porous media were with a flat free surface. A finite-difference algorithm considering the surface topography is presented for simulating seismic waves propagating in homogeneous porous media generating the coupled seismic and electromagnetic waves at seismic frequencies. The essences are the high order non-staggered grid finite difference method (Zhang and Chen, 2006) and the Biot's equation. It is shown that the stresses and velocities including the Darcy velocity and the grain velocity are directly updated at each time step and then the Runge-Kutta time integration is used. Our approach is tested by compared with independent solution for flat layered media obtained by the other independent method. We also show a numerical example of a hill shape surface model. The simulation in heterogeneous media and at all frequencies which is of more realistic sense will be discussed in next work.