Tectonic characteristics and activity history of the Dingmu Co fault-bounded basin in southern Xizang and its implications for the earthquake deformation zone of the MS6.8 Dingri earthquake on January 7, 2025

The M S 6.8 earthquake that struck Dingri County on January 7, 2025, has prompted extensive investigations into its post-seismic hazards, focal mechanism, and seismogenic structure. However, the absence of a systematic understanding the sedimentary framework, structural architecture, and other key geological characteristics of the Dingmu Co fault-bounded basin has hindered such efforts. Drawing on a 1:50,000-scale regional geological survey, we examined the sedimentary and structural features of the basin. We further integrated pre-earthquake audio-frequency magnetotelluric (AMT) and soil-radon survey data with optically stimulated luminescence dating of the fault fracture zones. Our results reveal that lacustrine deposits in the basin host abundant seismically induced soft-sediment deformation structures. The northern sector contains an east-west-trending half-graben, and the eastern sector is dominated by several north-south-trending strike-slip normal faults. AMT data have identified multiple concealed faults, and soil-radon measurements indicate heightened fault activity east of the central basin area. Shaped by the combined influence of the north-south-trending Dingmu Co strike-slip-normal fault system and east-west-trending Lhagoi Kangri Detachment System, the basin has undergone at least three episodes of intense tectonic activity since the Late Pleistocene, at ∼53.4, ∼37.1–32.2, and ∼9.2 ka BP, and is presently experiencing renewed deformation. Coseismic deformation associated with the January 7 event was concentrated at the intersections of north-south-, east-west-, northeast-, and northwest-trending faults. These results indicate the need to prioritize such intersection zones in future geological monitoring and disaster risk assessments. Overall, this study offers new insights for advancing seismotectonic research and understanding earthquake hazards in the Himalayan orogenic belt.