Seismic analysis of seabeds with irregular terrain under 2D oblique incident waves by finite/infinite element method

Abstract

Seismic response of seabeds with irregular terrain (i.e., canyons and hills) under oblique incident P- or SV- waves is analyzed by the finite/infinite element method (FIEM). Initially, based on the exact solution for a corresponding free field, the equivalent seismic forces for the solid-liquid site are calculated. Then, the solid-liquid coupling for the terrain slope boundaries is implemented with key numerical parameters selected for the FIEM. Furthermore, the adequacy of the solid and liquid meshes each was verified by comparing the solutions with existing ones for two extreme cases. Finally, the effect of irregular terrain on the seabed seismic responses was assessed for P- and SV-waves based on the 1999 Chi-Chi Earthquake. Key conclusions include: (1) The difference in the vertical acceleration aymax for SV-waves is the largest for the irregular seabed with one canyon and one hill under super-critical conditions. (2) The canyon shows more prominent amplification for the seabed responses near the seismic source for both P- and·SV-waves.·(3) Deeper liquid drastically amplify the difference in horizontal accelerations on two sides of irregular local terrain for sub-critical P-waves and near-critical SV-waves· Additional observations made for the numerical analysis are given inside the text.