Microseismicity detection and spatial-temporal migration in the Xinfengjiang reservoir, Guangdong, China

There have been many earthquakes in the Xinfengjiang Reservoir (XFJR) in the past 60 years since the M6.1 earthquake that occurred in 1961. In the XFJR, seismicity has migrated from southeast to northwest; however, the mechanisms for this migration have not yet been fully investigated. In this study, we used six years of data from both permanent and temporary seismic networks in the XFJR to detect >23,500 earthquake events using the EQTransformer. The minimum magnitude of completeness of the earthquake catalog decreased to −0.1, and the spatial distribution of the microearthquakes showed clear high-angle faults in the area, which included a new fault within the reservoir. The focal mechanism inversion results showed that earthquakes in the northwestern cluster changed from strike-slip to dip-slip faults with time whereas those in the southeastern cluster remained a mixture of strike-slip and dip-slip faults. Further analysis showed that spatiotemporal variation in the northwestern reservoir was due to earthquake migration along different faults. Overall, we concluded that earthquake in the whole XFJR area were affected by water infiltration along fault zone; Coulomb stress transfer may also contribute to the migration of earthquakes from southeast to northwest direction.