Frequency domain elastic wave modeling for polygonal topography using rotated average derivative diference operators

Modeling of seismic wave propagation in areas with irregular topography is an important topic in the feld of seismic exploration. As a popular numerical method for seismic modeling, the fnite diference method is nontrivial to consider the irregular free surface. There have been extensive studies on the time-domain fnite diference simulations with irregular topography; however, the frequency-domain fnite diference simulation considering irregular topography is relatively less studied. The average-derivative approach is an optimal numerical simulation scheme in the frequency domain, which can produce accurate modeling results at a relatively low computational cost. Nevertheless, this approach can only deal with the modeling problems with a fat free surface. To address this issue, we design a new frequency-domain fnite diference scheme by introducing the polygonal representation of topography into the average-derivative method. The irregular topog raphy is represented by line segments with various slopes. An extension of the conventional average-derivative diference operator in the local rotated coordinate system is used for formulating the spatial derivatives aligned with the topographic line segments. As a result, new average-derivative diference schemes are obtained for irregular topography. In this way, the average-derivative optimal method is generalized to the model with irregular topography. Numerical examples show the efectiveness of the presented method.