To study the effects of both free-surface topography and volume heterogeneities on seismic data, we develop a hybrid method which couples the boundary element (BE) method to model arbitrarily complex topography with the screen method for large volume of heterogeneous media. After briefly describing the principles of the two methods, we develop a boundary connection technique which is a critical step of coupling the BE method with the screen method. Its validity is tested by numerical

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... . Finally we apply the hybrid method to wave propagation in a model with both rough surface topography and irregular subsurface structure. Fig 2. Synthetic seismogram illustrating the effect of topography (a) and (b) the geometry of a model with a flat free surface (a) and the corresponding seismographs. (b). (c) and (d) The geometry of a model with the free surface of two upper-rises (c) and the corresponding seismograms (d).