Relationship between Landslides and Active Normal Faulting in the Epicentral Area of the AD 1556 M～8.5 Huaxian Earthquake,SE Weihe Graben(Central China)

In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.

The Volume Calculation Method of Rock Collapses and Loess Landslides Triggered by the 1556 AD Huaxian M81/2 Earthquake in Shaanxi Province, China

Accurate volume calculation of each individual landslide triggered by strong historical earthquakes can help understand the characteristics of the typical earthquake-induced landslides,thus providing significant information for the modification of the focal parameters of historical earthquakes.In this study,we select one rock fall and three loess landslides triggered by the 1556 AD Huaxian M8⅟􀄟earthquake,compute their volumes using the low-altitude high-precision Unmanned Aerial Vehicle(UAV)photogrammetry and landslide profile restoration methods.The results show that:①the whole influencing area of the Huangjiagou Rock Fall is approximately 3.03×105 m2 and the area of the collapsed rock accumulated at the slope foot is 3.33×104 m2,accounting for approximately 10%of the entire influencing range.However,the estimated volume of the collapsed rock is only 0.699×106 m3,indicating a rock fall with large influencing range but limited collapsed rock;②the geological form of thethree loess landslides are preserved intactly,with volumes of 0.283×108 m3,0.074×108 m3,and 0.377×108 m3.These important geological hazard relics reflect the strong vibrations and severe casualties in the meizoseismal area;③loess landslides are the key reason of the serious death toll in the hilly-gully loess area.Our new method can be used to estimate the influencing area and the actual volume of each individual landslide,and rationally evaluate the role of earthquake landslides in the disaster.In addition,quantitative research on secondary disasters triggered by strong historical earthquakes is beneficial for understanding the surface process and focal parameters of the earthquakes.