Insight into the Crustal Density Structure of Kumaon Himalaya, India, based on Gravity Modeling and Inversion

We introduce a new high-resolution gravity dataset acquired along a profile in the Kumaon Himalaya, extending from the Indo-Gangetic plains in the south to the Main Central Thrust (MCT) zone in the north. The Garhwal-Kumaon Himalaya, located in the central Himalayan region, has not experienced any great earthquake in the last 500 years. Therefore, it is essential to study the detailed crustal structure in order to better understand the stress and seismicity patterns in this area. Power spectrum analysis of the calculated complete Bouguer gravity anomaly (CBA) reveals two distinct crustal interfaces corresponding to the Moho and the Main Himalayan Thrust (MHT). To obtain the residual gravity anomaly related to the upper crustal structure, we apply the modeling-based gravity isolation technique, which involves isolating the gravity responses of deeper intra-crustal interfaces based on previous studies. We find that the sharp variations in the residual gravity anomaly align well with the surface geology of the region. Prominent signatures of major thrust boundaries, such as the Main Boundary Thrust (MBT), North Almora Thrust (NAT), and Main Central Thrust (MCT), are clearly identified in the residual gravity anomaly. We performed the wavelet analysis and particle swarm optimization (PSO)-based fault inversion to extract the fault geometries of different fault/lithotectonic boundaries from the residual gravity anomaly. These results are incorporated as a priori information to constrain the upper crustal structure during the forward modeling of the CBA. The detailed density structure gives insight into the geometries of the Moho, the MHT, and the lithotectonic boundaries for the study region. We will compare the crustal density model of the Kumaon Himalaya with the adjacent Garhwal Himalaya and discuss the crustal architecture in the context of the seismotectonics of the region.