3D tomographic imaging of the upper mantle beneath Eastern Ghats Mobile Belt, India: Imprints of a mantle plume

Abstract:

We present three-dimensional body wave velocity perturbation maps of the upper mantle beneath the Eastern Ghats Mobile Belt (EGMB) near the eastern coast of India, using teleseismic travel time tomography. Data recorded by 27 broadband seismic stations operated during 2015 to 2018 along two profiles covering EGMB and the adjoining Singhbhum and Bastar cratons were used for this purpose. We assemble P and S waveforms of 1157 teleseismic earthquakes and generate an accurate data set of 5876 P and 4834 S arrival times using multichannel cross-correlation and least squares. The 3D velocity perturbations are obtained by inverting the travel-time residuals at a 1.5⁰x1.5⁰ lateral resolution. The P and S wave tomograms show significant resemblance at various depths vindicating the robustness of data and inversions. We observe slow anomalies in the upper mantle beneath EGMB while the surrounding cratons show fast anomalies with respect to the IASP91 standard velocity model. The slow anomalies beneath EGMB seem to be associated with the Kerguelen plume activity, whose imprints have also been reported beneath Antarctica at locales juxtaposed with the EGMB in the geological past. The slow velocities dominant at 100 km depth also suggest a thin lithosphere beneath the EGMB compared to the surrounding cratons.