Lithospheric structure of the Kashmir basin and Panjal traps, western Himalaya: Insights from Seismic Imaging

We present a high-resolution image of the crust and lithospheric mantle beneath the Kashmir basin and surrounding Panjal traps of northern India that form the largest contiguous outcropping of the Permian (289 Ma) Himalayan volcanic groups, to a depth of 160 km, utilizing data from 22 seismological stations deployed in 3 phases between 2014 and 2024. The velocity structure is computed through joint inversion of receiver functions and Rayleigh wave group velocity dispersion data (period of 5-100s), alongside structural imaging using common conversion point (CCP) migration. The velocity image reveals several important crustal features: (i) Compared to global continent crust, the Kashmir-Panjal crust is more felsic with velocity of ~3.5 km/s to a depth of 40 km (ii) An anomalous feature of this region is a 25-30 km thick underplated high velocity layer (Vs>4.0 km/s) at the base of the crust. (iii) Moho depth is ~75 km in the southwestern part of the Kashmir valley, whereas it is ~65 km in the northeastern part. (iv) The Main Himalayan Thrust (MHT) is identified as a flat and low shear wave velocity (Vs ~3.1 and 3.4 km/s) structure located above crystalline Indian crust (Vs of ~3.6 km/s). In the shallow mantle, we observe a 30-40 km thick west dipping low velocity (4.3-4.4 km/s) channel at a depth of 90-120 km. This is the first report of such a low velocity channel in the western Himalaya. It’s genesis requires further investigation, currently in progress.