Surface Deformation Characteristics and Seismo-Tectonics of the 2025 Dingri Ms6.8 Earthquake in Southern Tibet

Destructive earthquakes and other natural disasters not only cause deterioration of the regional ecological environment, but also lead to soil erosion and local poverty, but also have a more direct impact on the loss of people's lives and property, as well as the destruction and deformation of ground buildings such as residential buildings. The Surface deformation characteristics, ground subsidence, and building collapse caused by the Ms 6.8 earthquake occurred in Dingri County, southern Tibet on January 7, 2025 were comprehensively analyzed through field investigations. The vertical displacement intensity along the Dingmu Co fault decreases from vertical displacement of over 185 cm at an altitude of over 5 500 meters in the north to vertical displacement of less than 120 cm at an altitude of over 4 200 meters in the east of Dingmu Co; The northern section has a westward drop, which is due to the overall descent of the upper plate of the Dingmu Co fault, with some sections descending in a stepped manner, resulting in steep slopes of up to 3 meters for ice water sediments and slope foot alluvial deposits in the ice eroded U-shaped valley; Occasionally, dry cow manure, Permafrost bulge, and huge ice debris being left displaced, indicating that this earthquake also had obvious strike slip characteristics. A Surface deformation with a north-south extension and an east-west width of up to 50 meters appeared in the alluvial deposits of the eastern Pleistocene in Dingmu Co, characterized by a central collapse and overall westward subsidence. The steep slope of the tensile rupture generally does not exceed 120 cm, and up to 50 cm squeezing uplift and seismic bulges are also developed at the leading edge of the tensile rupture, near the local section of Dingmu Co. The villages of Jiweng and Gurong, located in the center of the surface fissure, were the most severely affected by the Dingri earthquake. Except for a few cement and brick houses, most of the houses collapsed, making them the most severely affected villages in this earthquake. Based on the analysis of regional geological background, the Dingri earthquake is a shallow source destructive earthquake controlled by extensional structures. The upwelling of mantle thermal material in the Cenozoic era activated extensional structures represented by the north-south Dingmu Co strike-slip normal fault and the nearly east-west Tibetan southern detachment system, releasing energy at the intersection of these extensional structures and causing earthquakes.