Risk assessment of landslides induced by the Ms6.2 earthquake in Jishishan of Gansu province, China

Abstract

2023-12-18T23:59, an earthquake measuring Ms6.2 occurred in Jishishan County, China, causing serious casualties and directly leading to the occurrence of a large number of landslides. After the earthquake, multiple aftershocks increased the risk of collapse and landslides. Based on high-resolution satellite images before and after the earthquake, a Maximum Entropy model was constructed using visually interpreted landslide points and impact factors characteristics to evaluate the risk of landslide disasters after the earthquake. The conclusions of the study are as follows: 1) The main distribution of earthquake-induced landslide disasters is in the elevation zone of 1800-2300m, on sunny slopes with a slope gradient of 20–25°, which are mostly developed in the area 1.5 km away from the roads, 1.7 km away from the fault zones, and 5 km away from the earthquake center. The majority of the landslide occurred in cropland and loam areas with higher population density in the earthquake region. 2) Based on the contribution rate and replacement importance of the impact factors, test gain value, AUC value, and regularized training gain value, the main impact factors for landslide risk induced by the earthquake were comprehensively determined as follows: Distance from the fault zone, Elevation, and Population density. 3) Based on the constructed Maximum Entropy model, it is found that there is a good consistency between the extremely high and high risk areas of landslide disasters in the earthquake zone and the seismic intensity. Among them, the extremely high and high risk areas are mainly distributed in the intensity zone VIII, with an area of 5.368km², accounting for 77.82% of the total area of the extremely high and high-risk zones. The low and very low risk areas are mainly distributed in the intensity zones VI and VII, accounting for 92.80% of the total area of the study region. This paper constructs a Maximum Entropy model based on the analysis of the importance of impact factors to evaluate the risk of landslide disasters in the earthquake zone. The research results provide references for post-disaster reconstruction in the earthquake zone.