资源环境科技发展态势分析平台

We use seismic and geodetic measurements to optimize the fault geometry as well as coseismic slip distribution from the 2018 M-w 6.4 Hualien earthquake. We find that at least three faults were involved in the earthquake. The earthquake initiated from a south-dipping fault in offshore Hualien, and slip transferred into the main west-dipping oblique fault. The slip finally triggered movement of the east-dipping Milun fault at shallower depth and caused surface rupture. Although there is no offshore data constraints, our inverted slip distribution shows that the majority of slip occurred between 5- and 10-km depth on the main west-dipping fault, and 1- to 3-m slip on the shallower part of the Milun fault. Additionally, we process 5 months of postseismic deformation time series and find more than 5-cm postseismic displacement occurred along the Milun fault but is insignificant near the Coastal Range located south of the Hualien City.

Plain Language Summary Taiwan is one of the most tectonically active regions in the world. In eastern Taiwan, the Longitudinal Valley is located between the Eurasian Plate and the Philippine Sea Plate, and the rapid plate collision has cause high surface deformation as well as earthquake hazard in Hualien, the biggest city in northern Longitudinal Valley. In this study, we use measurements during the earthquake to study the fault geometry and fault slip due to the M-w 6.4 Hualien earthquake occurred in February 2018. Our inversion results show that at least three faults are involved in the event, including a south-dipping fault, a main west-dipping fault, and the east-dipping Milun fault located in the Hualien City. Our inverted fault slip at shallower depth is in agreement with field investigation after the earthquake. We also process 5 months of data to observe postearthquake surface deformation and find that there is more than 5 cm of displacement along the Milun fault, but insignificant displacement south of the Hualien City.