Dynamic process of the massive Xinmo landslide, Sichuan (China), from joint seismic signal and morphodynamic analysis

On 24 June 2017, a massive high-position landslide occurred at Diexi, Maoxian county, Sichuan, China, destroying the village of Xinmo with over 80 fatalities. Based on field surveys and DEM data before and after the landslide, the run-out of the landslide had a horizontal extent of 2400m and a vertical extent of 1200m and covered an area of about 1.48x10(6)m(2). Based on the pre- and post-landslide profiles, the landslide region can be divided into four zones: source area, erosion area, sliding area, and accumulation area. The volume and area of each zone were calculated from DEM data before and after the landslide. Because of the fragmentation and erosion of the landslide during movement, the landslide volume increased from 2.8x10(6)m(3) to 6.4x10(6)m(3); the fractional amount of volume expansion due to fragmentation (F-F) and entrainment ratio (ER) were 0.033 and 1.23, respectively. The velocity and acceleration of the Xinmo landslide were calculated through the inverted forces from seismic waves. The friction coefficients in each zone of the landslide during movement were also obtained, providing a useful parameter for numerical simulation modeling. An inverse relation was found between the absolute velocity and friction coefficient of each zone, demonstrating the existence of frictional velocity-weakening in massive extensive landslides. Based on frictional velocity-weakening, the steady-state apparent friction (U,sigma) as a function of absolute slip velocity U and normal pressure sigma was also obtained.