Incorporating topographic effects in surface wave tomography based on shortest-path ray tracing

We propose a new method to obtain 3-D shear wave velocity structures for regions with undulating topography based on surface wave dispersion data. In our method, we assume that surface waves propagate along a curved free surface, and the dispersion effects of these waves can be modelled as a frequency-dependent ray tracing problem. We use the shortest-path method to address off-great-circle propagation arising from inhomogeneous elastic parameters and topographic variations. We then apply our method to both synthetic and real-data inversions and demonstrate that ignoring topographic effects may significantly distort the inverted images. Finally, we analysed the accuracy of our method and provided a rule-of-thumb principle to quantitatively assess the need to account for topographic effects in surface wave tomography for a region.