Continental scale body wave tomography of India: Evidence for attrition and preservation of lithospheric roots

Abstract

We assemble P and S waveforms of 2301 teleseismic earthquakes registered at 413 broadband seismic stations spanning the Indian plate from the southern tip of India to the Himalayan collision belt and generate an accurate data set of 52,050 P and 30,423 S arrival times through the multichannel crosscorrelation approach. These traveltimes are then inverted to obtain 3-D P and S velocity structures of the subcontinent at a 2 3 2 lateral resolution. The heterogeneous nature of the Indian lithospheric mantle revealed in this study suggests that the lithospheric roots are not uniformly thick on a regional scale. The key cratonic segments of the Indian shield are characterized by pockets of high velocity anomalies ( 3%) at shallow depths (<300 km), with the diamondiferous regions like Wajrakarur revealing high shear wave anomalies down to 300 km. In contrast to the southern Deccan volcanic province (DVP), the northwestern DVP is underlain by low velocity anomalies at similar depths suggesting that the upper mantle retains imprints of Deccan volcanism which was facilitated by the reactivation of the rift systems.

Seismic Imprints of Plume‐Lithosphere Interaction Beneath the Northwestern Deccan Volcanic Province

“…Besides the low‐velocity anomaly beneath the Cambay, Kutch, and Saurashtra regions, we observed a high‐velocity layer of Vs ≥ 4.64 underneath the asthenosphere, at an average depth of ~166 km, beneath the Narmada Rift and Central India (Figures d and ). Similar findings were also reported by Singh et al () from body wave tomography. They suggested that the low‐velocity anomaly beneath DVP is restricted to the northern part only and the southern part of DVP is characterized by high velocity.…”

Mantle Deformation in the Eastern Himalaya, Burmese Arc and Adjoining Regions

“…Geochemical and geochronological data sets obtained using flood basalt rock samples from the Rajmahal‐Shylet‐Bengal traps (Figure ) show evidence of Kergulelen plume activity (∼116 Ma; Baksi, ; Basu et al, ; Kent et al, ; Ray et al, ). Imprints of a plume are also inferred from seismic tomographic images, where low‐velocity perturbations are observed beneath the Bengal Basin (Koulakov et al, ; Li et al, ; Singh et al, ). Ancient fabric preserved from the rifting episodes of India and Antarctica may result in a multilayered anisotropic medium, creating a vertical anisotropic heterogeneity.…”

Crustal velocity structure of the Neoarchean convergence zone between the eastern and western blocks of Dharwar Craton, India from seismic wide-angle studies

“…Several researchers have inferred post-Archean modifications, including wide-spread metasomatism of the Sub-Crustal Lithospheric Mantle (SCLM) of the Dharwar Craton (Griffin et al, 2009;Kumar et al, 2007;Oreshin et al, 2011;Kiselev et al, 2008;Singh et al, 2014). Oreshin et al (2011) showed that mantle S-wave velocity at depths less than 180 km is 4.4-4.5 km s −1 , much lower than the 4.7 km s −1 , typical for Precambrian shields.…”