Distribution and characteristics of loess landslides induced by the 1654 Tianshui earthquake, Northwest of China

Based on the loess landslides induced by the 1654 Tianshui Ms 8.0 earthquake, the relationships among the landslide distribution and seismic intensity, epicentral distance, fault distance, original slope angle, and the strike of loess ridges were analyzed to better understand the geometric, directional, and kinematic characteristics of loess seismic landslides. The results show the following: (1) The seismic intensity and fault distance are remarkably correlated with landslide area, landslide number density, and landslide areal density, which are essential factors controlling earthquake-induced landslide development in the Tianshui area. (2) The landslides triggered by the Tianshui earthquake predominantly developed on gentle slopes, and the dominant original slope angles of the landslides range from 10 to 20°. The Tianshui earthquake-induced landslides are mainly large scale, accounting for 62.01%. (3) The main sliding directions of the landslides are concentrated at 220°–230° and 260°–270°, which are relatively the same as the aspect of the original slope. The correlation between the main sliding direction of landslides, strike of the loess ridges, and relative epicenter azimuth shows that the sliding direction of the Tianshui earthquake-induced landslides is not only affected by the propagation direction of seismic waves and strike of loess ridges, the loess thickness and stratum structure may also serve as the main factors controlling the development of the landslides. (4) The equivalent friction coefficient (μ) of the landslides induced by the 1654 Tianshui Ms 8.0 earthquake is between 0.1 and 0.6, with an average value of 0.27. The empirical relationships between the landslide volume (V) and equivalent friction coefficient, maximum horizontal distance of the landslide (Lmax), and maximum vertical distance of the landslide (Hmax) show that the Tianshui earthquake-induced loess landslides have a significant scaling effect and are characterized by low-angle and long-distance slip. The findings of our study constitute a solid base for further research on the mechanism and risk assessment of seismic-induced loess landslides and provide engineering application value.