Seismic Anisotropy and Mantle Dynamics Beneath Maitri Station in Central Dronning Maud Land, East Antarctica: New Insights from Shear Wave Splitting Analysis of Core-Refracted and Direct S-phases

To elucidate the Gondwana supercontinent, we investigate mantle dynamics in Dronning Maud Land, Antarctica, using shear wave splitting analysis. This involves 12 S-phase teleseismic events and 38 core refracted phase (SKS, SKKS, PKKS and PKS) events, hereafter collectively referred to as XKS, recorded in the period 2013-17 (excluding noisy periods), at the broadband seismic station at Maitri, the Indian research station. The splitting parameters cI (fast polarization direction) and 6t (delay time) were estimated by cluster analysis and minimization of eigenvalues from covariance matrix of cI and 6t. Our XKS analysis, assuming a single layer of anisotropy, shows an average cI of 62 degrees and 6t of 1.1 sec. The S-wave analysis shows an average cI of 50 degrees and 6t of 0.97 sec. The cI values of the fast XKS and S-wave phases, having a north-east-south-west direction, are sub-parallel to the geological boundary of Schirmacher Oasis and the continental margin of East Antarctica. The observed margin-parallel XKS and seismic anisotropy at Maitri, which are also aligned to magnetic anomalies, correlate well with frozen lithospheric anisotropy, due to the major tectonic events, lineations and/or transtensional rifting at the breakup of Gondwana.