Seismic Hazard Assessment of the Mid-Northern Segment of Xiaojiang Fault Zone in Southwestern China Using Scenario Earthquakes

Abstract

ABSTRACT Seismic hazards in the vicinity of the mid-northern segment of the Xiaojiang fault zone were estimated from scenario earthquakes. Based on its history of earthquakes and activity data, the whole segment is considered capable of generating large earthquakes. The characteristics of previous ruptures and the geometric structures of the fault were used to establish seven scenario earthquakes with various strike and length properties. On the basis of focal mechanism parameters and the distribution of previous earthquakes, we determined the values of the source parameters for each scenario using empirical equations. We then used a stochastic finite-fault model to generate the ground motion from the targeted fault. The results show that the vicinity of the mid-northern segment of the Xiaojiang fault zone faces significant seismic hazards. The peak ground acceleration (PGA) values along the fault line are obviously larger than in other areas. Based on the recurrence interval theory, the Qiaojia–Menggu and Xiaoxinjie–Xujiadu areas have a high probability of being struck by large earthquakes in the near future. The results also show that the current design PGA for the near-fault area of the mid-northern segment of Xiaojiang fault zone might not be adequate.