Effects of the traction-free surface with a rugged topography on seismic wave propagation: Numerical modelling

Abstract

Understanding the impact of rugged topography on seismic data provides a means to design strategy to reduce or eliminate these effects from the seismic data. In this paper, the effect of rugged topography on synthetic seismic data is studied by using a finite-difference method with a velocity-stress staggered algorithm. Based on the FD algorithm, the imaging and vacuum methods are used to simulate the elastic wave propagation in flat and rugged traction-free interfaces for both acoustic and elastic models. Seismic waves in heterogeneous media with a rugged topography are numerically simulated, and the properties of the P-wave, S-wave, and Rayleigh wave along the topography are discussed. Shear waves, surface waves and their scattered events along the topographic surface are major contributions to the scattered energy propagating with slow velocities. Furthermore, effects of the topography on the synthetic seismic data are eliminated effectively by employing our proposed method based on full elastic wave theory. For removing the scattered waves from a near surface topography, the numerical simulation demonstrated that our method, taking into account shear and surface waves such as Rayleigh and Love waves, as well as P-waves, is very effective for synthetic data, provided the properties of the near surface with a rugged topography are known.