Seismic Parameters of the 2015 MW 7.8 Gorkha Nepal Earthquake in Eastern Nepal

This chapter gives seismic parameters of Mw 7.8 April 25, 2015 Gorkha, Nepal earthquake. The salient aspects of tectonics, slip modeling, geodetic deformation, rupture process, aftershocks, strong ground motion and damage caused are highlighted. NepalNepal has varied topography from low lands (EL 60 m) in the south to high mountains in the north including the World’s highest peak Mt. EverestMt. Everest (Fig. 2.1). It is in the center of the concave Himalayan belt with about 870 km in WNW-ESE direction and 130–260 km in N-S direction lying between latitudes 26.5°–32° N and longitudes 80°–88° E. Nepal occupies one-third of the active Himalayan belt having high seismicity in its northern part. Nepal has numerous active faultsFault in three major tectonicTectonics zones of Main Central ThrustMain Central Thrust (MCT), Main Boundary Thrust (MBT) and Main Himalayan (Frontal) Thrust (MFT). On April 25, 2015, an earthquake occurred near the Main Central ThrustMain Central Thrust. The Global Seismic Hazard Map (GSHAP) depicts that the NepalNepal region has a seismic hazard level of the order of 0.25 g for 10% probability in 50 years (Bhatia et al. 1999). Maximum hazard is in and around the MCT and the entire country has a hazard range of 0.1–0.3 g. The probabilistic seismic hazardProbabilistic seismic hazard map prepared by the National Seismological Center, NepalNepal shows a hazard of 0.1–0.4 g for a 500-year period at bedrock (Wijeyewickrema et al. 2015). DamageDamage is severe because of non-compliance of codes except for some modern buildings. Houses in villages and ancient towns of Kathmandu ValleyKathmandu valley are of brick or stone masonry with mud mortar, having little resistance to seismic loads.