3D crustal structure of Kumaun-Garhwal (central) Himalaya from joint inversion of surface wave and body wave dataset.

Understanding the crustal structure of the Himalayas and the geometry of the underthrusting Indian plate beneath the Himalayan arc provides crucial insights into regional tectonics and enhances earthquake hazard assessment in the region. This study focuses on the Kumaun-Garhwal Himalaya, a region that is proposed as a potential site for a future great earthquake. We obtained the 3D compressional wave (Vp), shear wave (Vs), and P-to-S wave velocity ratio (Vp/Vs) of the region. To achieve this, we employed joint inversion of body wave and surface wave datasets. This integrated approach overcomes the limitations of individual methods, providing a comprehensive view of the crustal structures. The analysis involved inverting the arrival times of 515 local earthquakes recorded at 41 broadband stations spanning the region and also analyzed continuous waveforms recorded by these stations between November 2006 and June 2008. The resulting crustal velocity structure and relocated earthquake hypocenters reveal a flat-ramp-flat geometry of the Main Himalayan Thrust (MHT). Furthermore, the findings offer critical insights into the crustal composition and its role in earthquake generation. These results enhance our understanding of the region's tectonic framework and contribute to better assessment and mitigation of seismic hazards in the Himalayan arc.

Keywords: Seismic tomography; Continental tectonics; Main Himalayan Thrust; crustal imaging.