Contrasting Crustal Signatures Across the 2021 MS6.0 Luxian (China) Induced Earthquake Revealed by Dense Seismic and Magnetotelluric Data

The 2021 Luxian earthquake has raised concerns about the seismic potential in the southern Sichuan Basin and highlighted the need to gain a further understanding of the area's seismic risks. To elucidate the underlying mechanisms driving the largest recorded hydraulic fracturing‐induced earthquake in China, this study investigates the local seismogenic environment of this notable event through an integrated seismic and magnetotelluric (MT) approach. Utilizing a linear Radon transform‐based mode‐separation method, we derived a 3‐D fine‐resolution velocity structure from dense seismic data. Corroborated by resistivity measurements using a co‐located MT array, our integrated data set provides compelling evidence for a complex upper‐crustal geological structure across the Huayingshan fault (HYS‐F). Apart from the low velocity and resistivity zones at 3–4 km depth within the HYS‐F, consistent with the location of fluid injection sites, we newly discovered a large‐scale low‐resistivity anomaly beneath the mainshock at depths exceeding 15 km. A comparable structural pattern emerges in the southeast of the HYS‐F, where the distribution and focal mechanisms of recently detected earthquakes, including and earthquakes, highlight the combined influence of shallow fluid injection and the ascent of deep metamorphic saline fluids in creating a breeding condition for seismicity. A prominent high‐velocity and high‐resistivity anomaly in the northwest, extending from the surface to depths exceeding 20 km, is potentially linked to intruded ancient materials originating from the lower crust. Our findings reveal that complex geological structures and dynamic processes strongly impact the occurrence and distribution of earthquakes in the Luxian earthquake region.