Strong Motion Data Analysis of the 4 April 2011 Western Nepal Earthquake (M 5.7) and its Implications to the Seismic Hazard in the Central Himalaya

In the present study, the strong motion data of the 4 April 2011 western Nepal earthquake (M 5.7) recorded by a dense network of 24 strong motion accelerograph stations have been used to estimate horizontal and vertical component of the peak ground acceleration (PGA) to better understand its bearing on the seismic hazard scenario of the Central Himalayan region. We assimilated attenuation curves using the observed PGA values and found that the zone is associated with higher H/V ratio in which the attenuation trend remains bimodal with one trend for closer distance up to 100-120 km, while the other trend corresponds to distances extending beyond 1000 km. We infer that the two different PGA trends have close bearing on the major tectonics and structural set-up of the region, which is possibly attributed to subsurface structural variation through which the seismic wave travels, suggesting changes of crustal heterogeneities beneath the source zone. The present work may improve the concept of ground motion model for evaluating seismic hazard for the Himalaya.