Seismic and geological evidence of hidden faults in the Yinpan Reservoir area based on a dense seismic array

This study constructed a high-resolution seismic catalog of 1,623 earthquakes that had occurred within 32 days in the Wulong Yinpan Reservoir area by using the deep-learning picking algorithm PhaseNet and the earthquake-location procedure Loc-Flow. A hidden fault extending up to approximately 20 km within the reservoir area was identified through analysis of precise earthquake locations and geological strata. We proposed that the increase in pore pressure caused by the intrusion of reservoir water in the sealed limestone layer results in induced seismicity along the hidden fault. Our finding sheds new insight on the importance of fluid pathways and fluid pressure in reservoir-induced seismicity and can facilitate seismic risk assessment in reservoir regions.