Mapping Seismic Hazard: A Comparison by Using Delineated Source Model and Spatially Smoothed Seismic Source Model

Abstract The fifth-generation seismic hazard map for China’s mainland (CSHM5) was developed based on the delineated seismic source models and the ground motion models (GMMs) for the peak ground acceleration (PGA) for four different seismic regions. In the present study, we developed a new set of GMMs as functions of the rupture distance or the closest distance to the projection of the rupture plane. The development of the GMMs is based on the projection method and GMMs from the NGA-West2 project. We then estimated, mapped, and compared the seismic hazard in terms of PGA and pseudo-spectral acceleration by using the new set of GMMs and other relevant GMMs, and two seismic source models—one used in developing CSHM5, which includes the fault orientation characterization and the other based on a spatially smoothed source model. The comparison of the estimated seismic hazard indicates that CSHM5 may significantly underestimate the seismic hazard. Part of this is likely due to the inclusion of an additional 15 km focal depth in the original GMM that is adopted for CSHM5. The comparison of the obtained standardized uniform hazard spectra (UHS) to the standardized response spectrum implemented in the current structural design code shows that the value of the latter is greater than that of the former for the natural vibration period less than about 0.1 s or greater than 0.4 s and this is reversed for the natural vibration period around 0.2 s. It is recommended that the use of UHS for design code making should be seriously considered, or at least, the shape of the current implemented standardized design spectrum could be improved.