Effect of 3D Topography on Physics-Based Earthquake Ground Motion characteristics.

This paper presents the effects of 3D conical topography on the pseudo-dynamically simulated ground motion characteristics. The simulation of pseudo-dynamic ground motion has been carried out using a fourth-order accurate staggered-grid time-domain 3D finite-difference method. In the case of numerical simulations, the radiation of seismic energy from the rupture plane as per Brune’s model as well as avoiding the coherency effects is a challenging job for the simulators. The randomization of slip, rise-time, and peak-time of the source time function and the rupture arrival time, as well as the incorporation of fault-roughness and damage zone, play important roles in seismic energy release from the rupture plane as well as in the reduction of currency effects on the high-frequency seismic radiations. Firstly, the ground motions have been simulated for a hypothetical strike-slip Mw 6.0 earthquake. The efficacy of the presented code has been validated with a good match of the computed average pseudo-spectral acceleration (PSA) using the simulated ground motion with that obtained using NGA-West2 GMPEs in the frequency range 0.1–5.0 Hz. The code has been able to correctly incorporate the rupture directivity effect. Further, the effect of 3D conical topography has been estimated with azimuthal coverage of receivers. The effect of the direction of the source on the topographic amplification has also been estimated. It has been observed that topography plays an important role in the amplification of earthquake ground motion. Also, the direction of the source plays an important role in estimating the pattern of topographic amplification.