Simulation of Long-period Ground motion: verification and sensitivity study on the 2013 Lushan Mw6.6 earthquake

Abstract

The eastern margin of the Tibetan plateau is adjacent to the Sichuan Basin, which is one of the areas with frequent large earthquakes. The important structures such as bridges and lifeline projects in the region is easily affected by long-period ground motion. It is significant to evaluate the long-period ground motion characteristics of destructive earthquakes in this region. In the first part of this study, the long-period ground motions of the 2013 Lushan Mw6.6 earthquake is simulated using the finite difference method, and three one-dimensional crustal velocity structures are used. We first compared the observed and simulated long-period ground motions of three models in terms of velocity waveforms, pseudo-velocity response spectra, and displacement response spectrum. We then analyzed the residuals of velocity waveforms between the amplitude of simulated and observed. In the second part of this study, the source parameters of rupture velocity, rise time, and stress drop are selected for sensitivity analysis. The results show that it is feasible to use the one-dimensional crustal velocity model of the Sichuan basin to analyze the long-period ground motion of the 2013 Lushan Mw6.6 earthquake. The amplitude of long-period ground motion decreases with the increase of rise time. The amplitude of long-period ground motion and the change of stress drop shows a linear relationship as a whole. The rupture velocity exceeds the shear wave velocity making the PGV distribution of long-period ground motion show spatial variability. In predicting scenario earthquakes, the uncertainty of parameters should be carefully considered. When some parameters are more sensitive to the long-period ground motion, more weights need to be given to these parameters to obtain reliable ground motion results.