Seismic hazard assessment for mainland China based on spatially smoothed seismicity

Abstract

Probabilistic seismic hazard assessment for mainland China is carried out by using spatially smoothed seismic source models obtained using the historical earthquake catalogue and two kernel smoothing techniques. The first one smooths the cumulative event count and the second one smooths the earthquake occurrence rate. For the analysis, the completeness of the catalogue is assessed and the k-mean seismic analysis results are used to aid the assignment of the regions. It is shown that the estimated parameters for the Gutenberg-Richter relation by using the maximum likelihood–based approach are consistent with those estimated by using the least-squares based approach by considering unequal observation periods. The developed seismic hazard maps indicate that the use of the smoothed source model obtained by smoothing the cumulative event count leads to spatially smeared seismic hazard. The use of the smoothed source model obtained based on smoothing the occurrence rate results in the seismic hazard map to have more spatial details. The seismic hazard assessment results indicate that, on average, the ratio of the 2475-year to 475-year return period values of PGA is about 2 and the ratio of the 2475-year to 50-year return period values of PGA is about 8. These ratios are associated with large scatters. A comparison of the normalized UHS and the Chinese design code recommended standardized design spectrum indicates that the latter is conservative as compared to the former for vibration periods outside of 0.1 to 0.2 s, and that the shape of the latter differs from that of former.