Nov 3, 2023, Nepal earthquake: Source mechanisms and structural response of Indo-Gangetic basin

Nov 3, 2023 Nepal earthquake is among the major earthquakes in the Himalayas since the 2015 Gorkha earthquake. The shaking from the earthquake was also felt strongly in the Indo-Gangetic basin of India, with a death toll of more than 150 people. This region is of particular importance because of three major structural elements: (1) the largest topographical variation in the world, (2) the largest crustal thickening and moho depth variation, and (3) the presence of Indo-Gangetic basin, which is one of the largest sedimentary basins in the world. In this study, we estimate the source mechanism of the earthquake obtained using regional and teleseismic broadband seismometers. This is also among the first applications of Raspberry Shake data for estimating the source mechanism, where we include its polarity information to scale the misfit function. We also present the uncertainty in the obtained moment tensor solution as a single quantity, estimated using a probabilistic approach. We further simulated the obtained moment tensor solution in a three-dimensional medium. The structural model used for simulation includes the basin model and the topographical variations. With this simulation, we visualize the effect of material properties and the contrast in material properties at the basin edges on the propagating seismic waves. We further compare peak ground velocity (PGV) values at basin and non-basin sites. This study is also important from the perspective of hazard assessment and mitigation in characterizing places with higher potential for ground shaking.