Seismicity characteristics of fault zones in Fujian area based on automatic seismic detection method

Driven by the tectonic loading of Taiwan and Taiwan Strait, there are several large Quaternary fracture zones in the Fujian area, with strong historical and current seismicity. We build a comprehensive seismic catalog with a new automatic workflow called PALM （phase picking, association, location, matched filter）, which combines STA/LTA and matched filter. PALM is applied to 10 month’s continuous data in 2015 of 88 stations from the Fujian Earthquake Agency. We recognized 919 template events and finally relocated 2 243 events after matching filter, among which 1 991 events with magnitude greater than M_L1.0, and it greatly expanded the catalog from Fujian Earthquake Agency in the range of M_L1.0−1.5. The depth of relocated earthquake events are distributed between 0 and 20 km, with most of them occurred within 10 km. The events are concentrated along Changle-Zhao’an fault zone and Yong’an-Jinjiang fault zone and showed obvious segmental activity. We detected more earthquakes than the catalog from Fujian Earthquake Agency, and the seismicity was stronger in the southwest section and weaker in the northeast section. The depth distribution along the fault zone became shallower from south to north, which was consistent with the change of Moho depth. Besides, we can see a highly clustered feature of seismicity at northwest section and slightly dispersed at southeast segment in Yong’an-Jinjiang fault zone, which forms a conjugate shape with Changle-Zhao’an fault zone. The repicked and relocated events in Fujian area was consistent with the characteristics of horizontal crustal deformation, which was stronger in south and east while weaker in north and west.