Paul and Ravi Kumar (2022) identified salient features of the mantle beneath the Indian Ocean and Ross Sea, by analyzing 8 global tomographic models. Their study indicates low velocity anomalies of dVs ~1.1% in the ~400–680 km depth range and inconsistent high velocity anomalies of dVs ≥ 1% at depths below 1600 km beneath both Indian Ocean and Ross Sea. A consistent low velocity structure throughout the mantle beneath the southwestern Indian Ocean and east Africa is associated with a plume from the African LLSVP. Forward modeling of the Geoid indicated that the E-W extent of the IOGL, influenced by upper mantle anomalies, could be precisely predicted, however, the N-S extent is underestimated since the lower mantle anomalies are inconsistent.
    Saha et al.(2021) mapped the 3-D shear wave velocity of the uppermost mantle beneath the Bay of Bengal using fundamental mode Rayleigh wave group velocities calculated along 21,600 crisscrossing paths from cross correlation of ambient noise as well earthquake seismograms. They obtained distinctly different lithospheres beneath the eastern and western Bay of Bengal, on either side of 86°E longitude. The western Bay of Bengal has > 120 km thick layered lithosphere and shear wave velocity of 4.7 km/s beyond 90 km depth whereas the eastern Bay of Bengal has thinner lithosphere (60–75 km) with minimum velocity of ~4.2 km/s, which is anomalously low for an old ocean.

3. Seismic Anisotropy, Crust and Mantle Flow

3.1 Crustal Deformation

3.1.1 Doda - Kishtwar Region, NW Himalaya