In this paper, we present a method to model acoustic wave propagation in the frequencydomainin the presence of free surface topography using the embedded boundary method. Theadvantage of this method is to solve for the pressure field at each frequency on regular finitedifference grids but with sub-cell resolution (up to 2nd order accuracy) for the irregular freesurface. The topographic free surface condition is implemented in 2nd order accuracy, as in theregular domain so that global 2nd order accuracy is guaranteed. We use the level set method toobtain the projection points and normal directions corresponding to the ghost points in thescheme in the irregular domain. The computational cost for solving the modified sparse matrixfor the pressure field increases very little compared to that for a flat surface. We havebenchmarked our solver with a 2-D Gaussian hill model and simulated wave propagating in amodified Canadian foothills model. This solver can be used as the forward engine in the fullwaveform inversion, and we are working underway to perform full waveform inversions withreal land survey data with considerable presence of surface topography.
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