Detection of microearthquakes and identification of their causative structures in the eastern offshore region of South Korea

A matched filter has been applied to continuous seismic records from the eastern offshore region of South Korea to identify small earthquakes undetected by routine processing. The resulting density of the regional earthquake catalog has increased by a factor of five relative to the detections reported by the Korea Meteorological Administration. High-precision locations of newly identified microearthquakes and previously located earthquakes cluster into streaks that delineate structures responsible for the seismicity associated with the Hupo Fault offshore of the southern Korean Peninsula. Microearthquakes in the northern and southern segments of the fault zone exhibit different behaviors: earthquakes in the northern segment occur at a regular temporal interval, while those in the southern segment occur in bursts. The identified fault system dips steeply to the west at shallow (