Eastward Dipping Style of the Underthrusting Indian Lithosphere Beneath the Tethyan Himalaya Illuminated by P and S Receiver Functions

Abstract

The Himalaya, extending for almost 2,500 km along strike, resulted from the India-Asia collision and convergence beginning at ∼65 Ma (DeCelles et al., 2014; Ding et al., 2005). Global positioning system (GPS) measurements estimate a shortening rate of ∼15 mm/year along the Himalaya (Zheng et al., 2017), leading to the development of an upper crustal fold-thrust belt. Three major north-dipping thrust faults, namely, the Main Frontal Thrust (MFT), Main Boundary Thrust (MBT) and Main Central Thrust (MCT), merge with the Main Himalayan Thrust (MHT) at depth. These thrust faults together with the South Tibetan Detachment System (STDS) divide the Himalaya from south to north into the sub-Himalaya, lesser Himalaya, higher (greater) Himalaya, and Tethyan Himalaya (DeCelles et al., 2014; Yin, 2006). Over the past decades, seismological images from various south-north profiles have clearly revealed that the Indian plate underthrusts the Himalaya along the MHT, which separates the overlying Himalayan fold-thrust wedge from the downgoing Indian lithosphere (

Shear‐Wave Velocity Reveals Heterogeneous Geometry of the Main Himalayan Thrust System and Deep Structure Beneath the Nepal Himalayas

“…Previous studies suggested that MHT could be identified as an anisotropic zone (e.g., Schulte‐Pelkum et al., 2005), or a weakening interface due to trapped water released from underthrusting sediments (e.g., Nábělek et al., 2009). It is noteworthy that multiple across‐strike receiver functions and reflection seismic studies in different parts of the Himalayas observed a sharp impedance boundary with high amplitude for MHT, implying that the nature of MHT could be reflected as a velocity contrast separating the Indian crust and the Himalayan orogenic wedge (e.g., Bai et al., 2019; Caldwell et al., 2013; Gao et al., 2016; He et al., 2018; Subedi et al., 2018; Xu et al., 2021), although this contrast could be weak. If this is the case, the geometry of MHT could be possibly delineated with seismic velocities.…”