Parameter estimation of ground-motion prediction model in Longmenshan region based on strong motion data

Based on generalized linear inversion scheme, strong motion data recorded from 2008 to 2015 is used to estimate source parameters, quality factor and local site amplification coefficient of 83 strong motion observation stations of Longmenshan region. The result shows that the stress drops of Wenchuan aftershocks tended to increase with time before occurrence of Lushan main shock, after which the stress drops of aftershocks decreased noticeably and then increased slowly with time. Furthermore, a significant high-frequency attenuation phenomenon was observed in source spectra of some aftershocks with M_S≥4.7. According to analyses on the temporal evolution tendency of stress drop, it is inferred that the phenomenon may be related with magnitude and the maximal source rupture slip rate of individual event. As a result, the quality factor of mountain and basins inverted in this study is Q（ f ）＝264 f ^0.75 and Q（ f ）＝223 f ^1.01, respectively. Finally, the obtained site amplification coefficients of 83 strong motion observation stations are classified into NGA site class A, B and C, and the average site amplification coefficients of the three site classes are calculated. The results indicate that the peak amplification coefficients of the three site classes are similar, and the peak platforms tend to develop to lower frequencies as the site becomes softer.