Monitoring induced seismicity in the Weiyuan shale gas field utilizing a dense array

Understanding the mechanisms of induced seismicity and assessing associated hazards is crucial for risk mitigation in shale gas production regions. From August 2022 to February 2023, we maintained a dense array of 245 nodal stations with an average spacing of ∼3 km, covering the entire Weiyuan shale gas field (WSGF), an actively exploited region that has experienced induced earthquakes up to M_w 5.0. Using the LOC-FLOW, we constructed a high-resolution earthquake catalog, precisely locating 29,669 events ranging from M_L − 1.35 to M_L 3.42 with a completeness magnitude (M_c) of −0.24. Seismicity formed five distinct clusters, with those in the southern WSGF closely surrounding hydraulic fracturing wells and exhibiting migration patterns consistent with pore-pressure diffusion. In contrast, northern seismicity displayed characteristics of fault reactivation, with events aligning with pre-existing geological structures. Additionally, we observed persistent seismic activity near the epicenter of 2019 M_w 5.0 event, suggesting a long-lasting aftershock sequence. Our findings emphasize the necessity of high-resolution seismic monitoring and long-term hazard assessment in shale gas fields. The results contribute to a better understanding of injection-induced seismicity and fault activation processes, providing valuable insights for risk mitigation and sustainable resource production in tectonically sensitive regions.