STUDY ON COSEISMIC DEFORMATION CHARACTERISTICS OF LOESS MUDSTONE LANDSLIDE BASED ON INSAR,UAV AND GNSS DATA -A CASE STUDY OF MS6.2 EARTHQUAKE IN JISHISHAN COUNTY, GANSU PROVINCE

According to the official determination of the China Earthquake Networks Center, a Ms6.2 earthquake struck Jishishan County, Linxia City, Gansu Province at 23:59 Beijing time on December 18, 2023. The focal depth was 10km and the epicenter was located at 35.7°N, 102.79°E, causing serious loss of life and property to the local people. After the earthquake, researchers from many domestic institutions combined field investigations and remote sensing technology to carry out basic characteristics, development patterns and susceptibility evaluation of co-seismic landslides, as well as research on the liquefaction landslide-mudflow formation mechanism in Caotan Village, Qinghai Province. However, there are few studies on the deformation and instability mechanism of hidden fractured mountains during strong earthquake, and there are very few in-situ monitoring data of GNSS and acceleration of landslides in the epicentral zone. This study takes the landslide in Zhaomuchuan Village(ZV), Guanting Town, Minhe County, Qinghai Province, which is located approximately 13 km from the epicenter within seismic intensity VIII, as a typical case. Using technology of D-InSAR based on LT-1 data, UAV tilt photography and GNSS with Accelerometer, combined with field investigation results, the study analyzes the coseismic deformation characteristics of loess and mudstone landslides during strong seismic events: a. The Zhaizi Mountain, where the landslide is located, exhibits typical loess tableland topography, open on three sides, with a dual structure of steep slopes composed of loess-gravel and mudstone. The high and steep terrain and the loess have a significant seismic amplification effect, with significant increase in tensile stress at the top of the slope during earthquakes. b. At the time of the earthquake, the landslide was significantly deformed, and the increment was 12.9~109.7mm, which tended to be stable within 24 hours. c. The in-situ acceleration monitoring data show that the topographic amplification effect of the landslide in ZV is significant, while the completely disintegrated lower part is not significant. d. The loess at the top of the slope has low tensile strength after the earthquake, making it susceptible to tension failure under stress. Differential weathering of mudstone and gravel in the middle of the slope makes it prone to collapse and falling rocks.