Seismic hazard of multi-segment rupturing for the Anninghe–Zemuhe–Daliangshan fault region, southeastern Tibetan Plateau: constraints from geological and geodetic slip rates

The Anninghe–Zemuhe–Daliangshan region is deformed by two parallel faults, i.e., the Anninghe–Zemuhe fault and the Daliangshan fault. A large seismic gap that characterizes the AZD region in the past 30 years has attracted significant research attentions to study the seismic hazard of these faults. However, it still remains a matter of debate whether the southern part of the Anninghe fault was ruptured with the Zemuhe fault in the 1850 M7.5 earthquake. The multi-segment rupture probabilities should be considered in the seismic hazard analysis. In this study, we divide the Anninghe fault, the Zemuhe fault and the Daliangshan fault into segments which are then used to build different multi-segment rupture combination models. First, we invert the fault slip rate in an elastic block model. Using both the geological and inverted geodetic slip rates as input constraints, we model the seismicity rates on the fault segments. Then, we compare the modeled seismicity rates with the historical earthquake catalog to test the validity of the models. The model, which does not consist of the multi-segment span the Anninghe fault and the Zemuhe fault, and the multi-segment combinations among the segments of the south Daliangshan fault and the north Xiaojiang fault, has the seismicity rates generally consistent with the fault slip rates and historical records. Finally, we use the compatible fault model to calculate the 475-year PGA values. Our modeled PGA values, from both the geological and geodetic slip rates, are averagely higher than those from the National Zonation Map. This methodology is more reasonable as it considers the fault slip rate and multi-segment rupture.