Shallow crustal architecture of the foreland Kumaon Himalaya analysing high-resolution seismic data

Ongoing under-thrusting between Indian and Eurasian plate poses a serious concern to millions of human lives residing in the foreland Himalayan. A devastating earthquake in the Central Seismic Gap (CSG) is anticipated in various studies with a possible estimated slip of ~10 m, thereby a thorough analysis of the foreland set up is essential. Present study aims the Kumaon Himalaya of the CSG using the high-resolution seismic sections along profiles PGR4, PGR5 and PGR6. Profiles PGR4 and PGR5 trend N-S direction across the Kaladungi Fault (KF) and Himalayan Frontal Thrust (HFT), whereas the PGR6 trends E-W in the Indo-Gangetic plain. Here we mostly observe Siwalik formation and alluvial deposits of the Dabka and Baur rivers. PGR4 and PGR5 clearly show evidence of south verging faults that displace the Siwalik formation. We observe Upper, Middle and Lower Siwalik rocks at ~0.82 and 0.62 s, ~1.38 and 1.27s, and ~1.88 and 1.85 s TWTT in the footwall and hanging wall sides of KF, respectively. Sedimentary deposits near the KF is highly fractured and host multiple traces of the Fault among which two reach to the surface inferring these are active. We further observe highly folded top sediments with evidence of fault bend folding at North of the KF. In the Indo-Gangetic plain, we observe gentle folding in the Lower Siwalik deposits and trace of a south verging fault that meets the Main Himalayan Thrust (MHT) at ~3 s TWTT displacing the Lower Siwalik deposits by ~ 0.0368 s TWTT. Evidence of such folding and displacements in the formation reveal that foreland Himalaya is conducive to rupture propagation of any major earthquakes developed along MHT over the CSG.