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Seismic anisotropy beneath a transect of Kumaon Himalaya using shear wave splitting analysis

Authors

Krishnavajjhala,  Sivaram
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Gupta,  Sandeep
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Kumar,  Sudesh
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Bnv,  Prasad
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

M Sai,  Dixith
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Ali,  Saneesh
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Rawat,  Vishal
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Krishnavajjhala, S., Gupta, S., Kumar, S., Bnv, P., M Sai, D., Ali, S., Rawat, V. (2023): Seismic anisotropy beneath a transect of Kumaon Himalaya using shear wave splitting analysis, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-2017


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018833
Abstract
We explore the pattern of seismic anisotropy beneath a ~300 km transect in the Kumaon Himalaya, an active, orogenic region formed by the collision between the India-Eurasian plates, and carrying world-wide attention for its mysterious geometry and seismic potential. Applying the shear wave splitting analysis of the teleseismic core-refracted phases (SKS, SKKS, PKS and PKKS) on a linear profile of 32 broadband seismograph stations, we uncover the signatures of enigmatic strain histories and mantle dynamics. The measured shear wave splitting parameters i.e. Φ (Fast Polarisation Direction, FPD) and δt (Delay Time, DT) carry extraordinary information of the anisotropy formed through the complex mantle-deformation. We observe a strong dependence of the splitting data on the back-azimuth directions, which fits fairly well with a two-layer anisotropy model, with the lower layer having a low dipping angle at most of the stations. We present a geodynamic model depicting the preserved and the current situation of the compression-forces at the India-Asia collision zone. Incidentally, the mean Φ are primarily sub-parallel to the North East (NE)-oriented absolute plate motions (APM), and nearly orthogonal to the major geological boundaries in the Higher Himalaya. In the Lesser Himalaya, the mean Φ are nearly orthogonal to the APM and are sub-parallel to the surface expressions of major geological features. Similarly, we observe a wide variation in the mean δt. Our detailed analysis indicates a predominantly asthenospheric source of anisotropy, and a possible slab-tearing for this segment of the Kumaun Himalaya.