For seismic waveform inversion of body waves, the free surface is usually neglected on<br>grounds of computational efficiency. Subsurface parameters are simply extended in the air,<br>and sources and receivers are embedded in the model at their true locations. Many synthetic<br>studies have shown that this is an acceptable approximation if the surface is flat and,<br>naturally, surface waves are excluded from the inversion. In this study, we investigate the<br>effects of ignoring P wave scattering from irregular topography in acoustic waveform<br>inversion.