Spatial variations of crustal thickness and Poisson's ratio in the northeastern region of India based on receiver function analysis

Abstract

Crustal configuration beneath the northeastern region of India has been investigated with the help of receiver function (RF) analysis of teleseismic earthquakes recorded by 19 broadband seismological stations. We adopted the H‐k stacking method to estimate crustal thickness and Poisson's ratio beneath each recording station. The study reveals a large variation in crustal thickness and Poisson's ratio which are correlated with the complex geology and tectonics of the region. The crust is observed to be thinner (36.5–41.6 km) beneath Bengal Basin, Shillong Plateau, and the Brahmaputra valley compared to the Indo‐Burma Ranges (IBR) (~40–54 km) and Arunachal Higher Himalaya (TAWA station, ~45 km) and Sikkim Himalaya (GTK station, ~46.5 km). A large variation of Poisson's ratio is observed in the region (~0.230–0.306). Poisson's ratio is generally low‐to‐intermediate in the Shillong‐Mikir Plateau, Bengal Basin, and the Brahmaputra Valley, while it is intermediate‐to‐high in the Tripura Fold Belt and the northern part of the IBR. The high Poisson's ratio in the Tripura Fold Belt is due to the presence of basaltic basement rock and clay minerals existing in the sedimentary rocks, whereas the presence of partially serpentinized rock in the ophiolitic mélange complex causes a high Poisson's ratio in the IBR.