Response of the Laprak, Nepal, landslide to the 2015 Mw 7.8 Gorkha earthquake

Coseismic displacements estimated from comparison before-and-after satellite images suggest that the large and intermittently active landslide upon which the village of Laprak, Nepal, was built moved a geometric mean of 80 cm (95% mean confidence interval of 74-86 cm) or less during the 2015 M-w 7.8 Gorkha earthquake. The village was located about 6 km from the earthquake epicenter. We used published geotechnical and topographic data collected as part of a previous study of the landslide, publicly available earthquake information, and a physically plausible range of pre-monsoon dry season pore-pressure coefficients to constrain Monte Carlo simulations based on six published simplified Newmark models of coseismic displacement in natural slopes. Kolmogorov-Smirnov statistics show that five of the models produced coseismic displacement distributions in good to marginal agreement with our satellite image measurements. A seventh result obtained by combining results from the six individual models to balance the strengths and weaknesses of each also produced good agreement. The agreement between our observed and simulated results suggests that simplified Newmark models may be reliable tools for reconnaissance level earthquake hazard assessment in mountainous areas if probabilistic approaches are used to account for input parameter uncertainty.