Coseismic landslide hazard assessment for the future scenario earthquakes in the Kumaun Himalaya, India

Abstract

The coseismic landslide is one of the important hazard phenomena in the hilly and seismically active mountainous region. It is, therefore, essential to map the areas susceptible to coseismic landslides, especially for the seismically active region. In the present work, the probabilistic assessment of coseismic landslides has been carried out for Goriganga valley located in the Kumaun Himalaya, India, which lies in the highest seismically active zone of the seismic zoning map of India. Several studies suggest that this region is prone to a great future earthquake of Mw ≥8.0. In this context, mapping of the coseismic landslide has been made for the future scenario earthquakes of 7.0, 8.0, and 8.6 Mw using modified Newmark’s analysis. The modified Newmark’s analysis provides the permanent displacement of the potential landslide, by integrating (1) joint strength of rock mass, (2) critical acceleration of the slope, and (3) peak ground acceleration of the region. Newmark permanent displacement has been estimated, which provides the distribution of predicted slope failure in the area. It has been observed that 41% of the area exhibits ˃40 cm Newmark’s permanent displacement corresponding to Mw 8.6 earthquake and thus susceptible to failure, followed by 8.0 and 7.0 Mw earthquake with 36 and 14% of the area susceptible to the coseismic landslide, respectively. Further, the maximum permanent displacements for the simulated earthquakes of Mw 7.0, 8.0, and 8.6 are 76, 279, and 502 cm, respectively.