| Abstract Submission No. | ABS-4.1-0134 |
| Title of Abstract | Decoding the Anisotropic Lithosphere of Northeastern India through Ambient Noise and Receiver Function Techniques |
| Authors | Dhiraj Kumar Singh*, Mohit Agrawal, Hitank Kasundhan, Om Prakash Mishra, Mrinal K. Sen |
| Organisation | Indian Institute of Technology (Indian School of Mines) Dhanbad |
| Address | Department of Applied Geophysics, IIT(ISM) Dhanbad, Jharkhand, India Pincode: 826004 E-mail: dhirajs0208@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Northeastern India represents a geodynamically complex zone shaped by the interaction and evolution of multiple tectonic regimes. The region has long been at the centre of debate concerning its past and present tectonic configuration. Bounded by the Eastern Himalaya in the north, the subducting Indian plate toward the east, the uplifted Shillong Plateau in the centre, and an intricate network of faults and lineaments, it provides a natural laboratory to probe lithospheric processes. In this study, we utilize cross-correlation of continuous ambient noise seismic data recorded between 2015 and 2020 to extract empirical Green¿s functions representing interstation impulse responses. Dispersion measurements from these Green¿s functions are inverted to construct Rayleigh wave group velocity tomograms in the 7¿25 s period range, enabling imaging of lithospheric structure at varying depths. Additionally, receiver functions obtained through Multi-Taper Correlation are subjected to harmonic decomposition to investigate major crustal and lithospheric interfaces beneath stations distributed across the region using data from 2011-2020.Results from ambient noise tomography highlight prominent physiographic and geological contrasts at shorter periods (≤10 s). At longer periods, the Dauki Fault emerges as a north-dipping structure with a near-constant dip to ~20 km depth (period ~16 s), steepening further at greater depths. The tomograms also provide evidence of oblique subduction of the Indian plate beneath the Burmese plate near ~25°N, reflected by variations in crustal thickness and velocity gradients. Complementary receiver function harmonic analysis reveals tectonic support for the Shillong Plateau, strain heterogeneity near the Kopili Fault and Indo-Burma Ranges. The coexistence of a shallower Moho, and stress-oriented perpendicular to the anisotropic tilt direction observed on Shillong Plateau, validates the hypothesis of a tectonically uplifted plateau. The results imply a crust¿upper mantle interaction that generates 2D entrained flow along the subduction system, coexisting with the 3D toroidal flow beneath the Burmese arc. |
| Keywords | Ambient Noise Tomography, Cross-Correlation, Receiver Function, Harmonic Decomposition, Northeast-India, Dispersion |