On the Ground-Motion Models for Chinese Seismic Hazard Mapping

The ground-motion models (GMMs) used to map seismic hazard in China were developed based on the so-called projection method, assuming relations of a pair of predicted macrointensities and of a pair of predicted ground-motion measures in two different regions. The use of such a method is necessary because the ground-motion records of a large number of strong earthquakes are lacking in mainland China, although the catalog of historical Chinese earthquakes is relatively rich. A critical review of the GMMs adopted to develop the third-, fourth-, and fifth-generation Chinese seismic hazard maps (CSHMs) for mainland China suggests that some of the information used to project these models, such as the earthquake magnitude interpretation and GMM for the macrointensity, may need additional justification, and that the standard deviation (sigma) of the GMMs may be low. Also, new GMMs applicable to mainland China are developed based on the projection method and a set of the GMMs from the Next Generation Attenuation relationships. The results obtained using newly projected GMMs and seismic hazard analysis indicate that the ratio of the return period values of the peak ground acceleration obtained using the newly projected GMMs and using the GMMs adopted for the fifth-generation CSHM is about 1.35 for a return period range from 50 to 2475 yr. Part of this increase is attributed to the differences in the standard deviations of residuals for the newly projected GMMs and the adopted GMMs used to map seismic hazard for mainland China. The results also suggest that the shape of the adopted seismic design spectrum in Chinese structural design code differs from the uniform hazard spectra obtained based on the newly projected GMMs for simple seismic source zones.