Co-seismic landslide hazard assessment of Uttarakhand state (India) based on the modified Newmark model

Co-seismic landslides are the most dangerous geological hazards in seismically active mountainous regions. These landslides cause damage to roads, drainage pipelines, buildings, agriculture, and loss of human lives. It is crucial but difficult to precisely map the hazards resulting from earthquake-induced landslides. Newmark's approach is widely used to determine the permanent displacement of a probable sliding mass and simulate the mechanism of seismically-induced slope failure. The present study assesses co-seismic landslide hazards for Uttarakhand state (India), which falls under the highest seismically active zones as per the seismic code of India. It proposes an improved Newmark's approach aby incorporating rock joint shear strength parameters and the size effect of possible sliding surfaces. Static factor of safety and critical acceleration maps were prepared for the study area by combining various geological, geotechnical, and topographical parameters. The ground motion parameters were determined in terms of surface-level Arias Intensity. Newmark permanent displacement map was prepared by taking critical acceleration and Arias Intensity as input parameters. Finally, the modified Newmark's model results were compared with the conventional Newmark's model using the area under curve (AUC) analysis. This assessment approach can be used effectively to forecast the area affected by co-seismic landslide hazards and prepare guidelines for major infrastructure projects and post-disaster damage studies.