Analysis of the GNSS deformation of the 2025 Xizang Dingri M6.8 earthquake

The study utilized GNSS observation data from 1999 to 2024 to investigate the crustal deformation characteristics near the epicenter of the Dingri earthquake. The results show that the GNSS horizontal velocity value at the Dingri earthquake epicenter is about 25.9 mm/year, and the vertical velocity value is close to zero. The vertical velocity field indicates that most of the study area is subsiding, while the rift area is uplifting, and the Shenzha-Dingjie fault zone is in an uplifting area with a significant uplift gradient. The maximum shear strain rate and the second invariant of the strain tensor at the epicenter are 36 × 10⁻⁹/year and 56 × 10⁻⁹/year, respectively. The surface expansion rate field suggests that the earthquake occurred in a region of compressive deformation. The historical earthquake stress change distribution indicates that the Coulomb stress change loading value at the epicenter of the Dingri earthquake is 1.549 bar, exceeding the stress triggering threshold. This indicates that historical earthquakes promoted the occurrence of this event. The central and western sections of the South Tibetan Detachment System fault zone and the middle section of the Shenzha-Dingjie fault zone are located in high-strain value areas and postseismic stress loading regions. The seismic risk in this region should be closely monitored in the future.