INVENTORY AND SPATIAL DISTRIBUTION OF LANDSLIDES IN Ⅸ-Ⅺ HIGH INTENSITY AREAS OF 1920 HAIYUAN (CHINA) M8.5 EARTHQUAKE

The Haiyuan M_S8.5 earthquake on December 16, 1920, occurred at the loess plateau. It triggered a large number of landslides. The landslides directly caused a large number of casualties. In recent years, there have been some special studies on landslides triggered by the Haiyuan earthquake. However, most of these studies have limitations on their local study areas or individual landslides. There are few detailed and comprehensive results about landslides triggered by the earthquake. This situation has become an obstacle to understand the overall incidence and severity, spatial distribution law of the Haiyuan earthquake-triggered landslides. In this study, we carry out the visual interpretation of landslides in the high seismic intensity(Ⅸ-Ⅺ)areas of Haiyuan earthquake based on Google Earth platform, as well as analyze the relationship between landslides and several influence factors. Results show that the earthquake triggered at least 5384 landslides, which have a total landslide area of 218.78 km². The highest density of landslides is located at the NW part of seismic intensity Ⅸ circle. Through analyzing the relationship between these landslides and topography, earthquake and geological factors, it is found that elevation 1700~2000 m registers the largest landslide number and density. Most landslides are concentrated in the slope angle range of 15°~25°whereas the number density of landslides increases with the increase of slope angle. The lower the slope position is, i.e., the closer to rivers, the greater the density of the landslides. The areas with Cenozoic strata underlying, especially the Quaternary loess covered areas, register most of the landslides and the high density of landslides. This study provides a scientific reference for exploring the law of the occurrence of seismic landslides and reduction and mitigation of earthquake-triggered landslides in loess area.