Assessment of the effects of historical strong earthquakes on large-scale landslide groupings in the Wei River midstream

Regional active tectonics and historical earthquake records indicate the importance of the triggering effects of historical strong earthquakes on groups of large-scale landslide occurrences in the Wei River midstream section. In this study, a method to assess the triggering effects of historical earthquakes on regional large-scale landslides is presented. The greatest epicentral distances of seismically induced landslides were calculated. The triggering effects of four key historical strong earthquakes with epicenters within 300 km of the Wei River midstream section were analyzed; these are the Ms 7.0 Qishan earthquake of 780 BCE, the Ms 8.0 Tianshui earthquake of 1654 CE, the Ms 8.25 Huaxian earthquake of 1556 CE, and the Ms 8.5 Haiyuan earthquake of 1920 CE. Taking the Qishan earthquake as an example, a seismically induced landslide displacement and hazard assessment method based on the Newmark displacement model was developed. The degree of spatial matching of the results for historical-earthquake-triggered landslides and the distribution of actual large-scale landslide deposits were compared quantitatively using the success rate curve method. The results show that of the four historical earthquakes, the Tianshui earthquake had the strongest effect of inducing large-scale landslides regionally along the Wei River midstream section.