Characteristics And Hazard Assessment Of Landslides Triggered By Strong Earthquakes In The Loess Area Of The Hexi Corridor

The loess seismic landslide is a kind of the typical earthquake geological disasters in the loess region,and it is also one of the most catastrophic geological disasters in the loess region of China.It is also the main natural disaster in the loess region.The Hexi Corrido is the gateway and land fortress under the strategic planning of China’s “the Belt and Road.”.And its earthquake safety is related to China’s national strategic security.The genesis of loess distributed in Hexi Corridor includes aeolian,alluvial and moraine deposits,etc.,and its physical and mechanical properties are different from those of typical loess in Loess Plateau.At the same time,due to the influence of loess sediment thickness,topography,hydrological conditions and other factors,there are great differences between loess seismic landslides in Hexi Corridor and typical loess seismic landslides in Loess Plateau.With the deepening of international cooperation of "the belt and road initiative" and the steady implementation of national strategies such as "transportation power" and "rural revitalization",the risk assessment of loess earthquake landslide in Hexi Corridor needs to be carried out urgently.Combined with field investigation and landslide recheck,the landslide distribution has been revealed through the visual interpretation of remote sensing images of main loess distribution areas in Hexi Corridor.The relationships between landslides and various influencing factors have been explored through spatial analysis of geographic information science(GIS).Furthermore,comparisons have been made between the1927 Gulang earthquake landslides and other seismic landslides in the Loess Plateau through macro and micro soil mechanics research methods.Then the differences of the comparisons are clarified.The contribution weight model and the analytic hierarchy process are used to obtain the landslide hazard assessment results under different exceeding probability levels of the study area.The main conclusions are as follows:(1)The total number of landslides induced by the 1927 Gulang earthquake in the study area is 807,with a total area of 256.14 km2 and an average area of 0.32 km2 per landslide.According to the statistical results,most of the seismic landslides in the study area are medium and large landslides.The number of landslides with an area larger than1 km2 is small,accounting for only 7.56% of the total landslides.The largest number of landslides has an area between 104 m2 and 106 m2,accounting for 91.82% of the total landslides.(2)In the study area,the loess seismic landslides are controlled by multiple factors,including seismic intensity,slope angle,elevation,slope aspect,fault belt,water system and relative elevation difference.The number of seismic landslides is the maximum in the region with a seismic intensity of Ⅹ.The slope angle of(10°,40°],the elevation of(2000m,3000m] and the relative elevation difference of(100m,300m] are all the high-incidence areas of the seismic landslides.The dominant slope aspect of seismic landslides is the S direction.The closer to the fault belt and river,the seismic landslides are significantly affected by the fault belt and water system.(3)Compared with the typical loess seismic landslides,the loess seismic landslides in the study area have the characteristics of smaller scale,larger slope angle,and larger relative elevation difference,which is mainly related to the small distribution thickness of loess layer and large topographic relief in the study area.In terms of physical properties and microstructure,the loess in the study area is relatively dense and dry and the strength of loess structure in the study area is greater than that of typical loess in Loess Plateau.Due to this,the intensity of ground motion,which could induce the landslides,is greater.(4)The results of landslide hazard assessment in the study area show that the moderate and severe risk areas are mainly distributed in the western,northwest,and eastern parts of Tianzhu Tibetan Autonomous Region and the southwestern and southern parts of Gulang County.Slight risk areas are mainly distributed in the southern parts of Liangzhou District and the central and southern parts of Gulang County.