Brief Communication: Landslides triggered by the M_s = 7.0 Lushan earthquake, China

Abstract. Earthquake-triggered landslides have drawn much attention around the world because of the severe hazards they pose. The 20 April 2013 M_s = 7.0 Lushan Earthquake, which occurred in the Longmen Shan region in Sichuan province, China, triggered more than 1000 landslides throughout an area of about 2200 km², and completely blocked many roads and exacerbated overall transportation problems in the mountainous terrain. Preliminary landslide inventory is complied immediately following the earthquake, mainly based on the high-resolution remote sensing images. At the same time, the distribution of these landslides is statistically investigated to determine how the occurrence of landslides correlates with distance from the earthquake epicenter, slope steepness, seismic intensity and rock type. Statistic analysis is conducted using landslide point density (LPD), which is defined as the number of landslides per square kilometer. It is found that LPD has a strong positive correlation with slope gradients and a negative-exponential decline with the distance from the epicenter. The higher LPD values occur in younger strata systems like Quaternary and Tertiary sediments in the study area. Spatially, the triggered landslides are controlled by the causative faults and mainly concentrated around the epicenter. All the landslides are located within the area with seismic intensity ≥ VII and in line with seismic intensity. Generally, LPD value decreases with increasing distance from the epicenter, and sometimes landslides are densely distributed along the roads in the mountainous region. Also, this study reveals that the empirical relationship between distance and seismic magnitude is more suitable for estimating the landslide concentration area during the Lushan earthquake compared to other methods.