The Complexity of the 2018 M w 6.4 Hualien Earthquake in East Taiwan

Abstract

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.