The influence of ground shaking on the distribution and size of coseismic landslides from the Mw 7.6 2005 Kashmir earthquake

Abstract

Understanding the conditions that governed the distribution of coseismic landslide frequency and size from past earthquakes is imperative for quantifying the hazard potential of future events. However, it remains a challenge to evaluate the many factors controlling coseismic landsliding including ground shaking, topography, rock strength, and hydrology, among others, for any given earthquake, partly due to the lack of direct seismic observations in high mountain regions. To address the dearth of ground motion observations near triggered landslides, we develop simulated ground motions, including topographic amplification, to investigate these key factors that control the distribution of coseismic landslides from the Mw 7.6 2005 Kashmir earthquake. We show that the combination of strong peak ground motions, steep slopes, proximity to faults and rivers, and lithology control the overall spatial distribution of landslides. We also investigate the role of topographic amplification in triggering the largest landslide induced by this earthquake, the Hattian Bala landslide, finding that it is amplified at the landslide initiation point due to the trapping of energy within the ridge kink as it changes orientation from E to NE. This focusing effect combined with predisposing conditions for hillslope failure may have influenced the location and size of this devastating landslide.