AMPLIFICATION OF PLANE SH WAVES BY A CONVEX TOPOGRAPHY BASED ON THE TI MEDIUM MODEL

Forward modeling is an important method in simulation of seismic wave propagation in some medium. This paper adopts the indirect boundary element method (IBEM) to conduct the forward modeling to study the scattering problem of incident SH waves in transversely isotropic (TI) convex topography with various parameters, in order to give explicit interpretations to the amplification effect of this problem. The amplification effect is reflected by the ratio of the displacement amplitudes on the surface of the convex site and the bedrock outcrop. Combined with the precise dynamic matrix of layered TI half space and dynamic Green function of the site under evenly-distributed diagonal loads, the IBEM has much higher preciseness. The results of the incident SH waves scattering problem in a convex topography are provided in frequency and time domain respectively. Study in frequency domain implies that the amplification spectrum and spatial distribution of the displacement amplitudes are significantly affected by the soil TI properties, which indicates the change of TI medium parameters would cause fluctuations of the dynamics characteristics in both the convex part and the soil. Thus the dynamic interaction between them would change. Study in time domain shows that the propagation of SH wave around the convex topography depends on the values of TI medium parameters and propagation direction. Snapshots of instantaneous displacement amplitudes show the propagation process of incident waves, transmitted waves, reflection waves and scattered waves. The propagation of scattered waves generated at the convex corners is‘semi-elliptical’type in TI medium, but‘semi-circle’type in isotropic medium.