Complex tectonic imaging of orogenic front in Southwestern Taiwan

Abstract This study conducts annual microseismic surveys along major active faults and their surrounding areas in the southwestern Taiwan. Most fault activity in this region occurs within the upper crust at depths of approximately 10–15 km. According to previous studies, the study area is located in the area known as the Chishan Transform Fault Zone (CTFZ) which exhibits left-lateral strike-slip faulting in the northwest-southeast direction. Based on data of three recent moderate earthquakes in this area, the spatial distribution of aftershocks is more or less parallel to the CTFZ, but the overall trend has no correlation with previously mapped faults. Therefore, the primary goal of this study is to establish a microseismic monitoring network and collect seismic data to obtain a three-dimensional velocity model that can represent the seismogenic zone. Therefore, this study analyzes the distribution of micro-earthquakes and focal mechanisms to determine the tectonic characteristics of several active faults in southwestern Taiwan. The correlation between seismicity, local tectonic stress and the velocity structure is used to define the complete contours of the seismogenic structures. The results are integrated to explore crustal deformation and seismic structures along the frontal orogenic belt in southwestern Taiwan. The results also provide insights for earthquake hazard assessment.