Figure 1. Pn velocity of the upper mantle of the Indian shield
and adjoining regions obtained on a grid of 1\(^{\circ}\)×1\(^{\circ}\) size. Pn anisotropy
results with magnitudes are also superimposed to illustrate the
correspondence between anisotropy patterns and the major velocity
anomalies. KHT- Kerguelen hotspot track. The gray arrow in the top right
corner indicates the present-day Indian plate motion direction. (From
Illa et al., 2021a) (Reprinted from Tectonophysics, Vol 813, Bhaskar Illa, K.S. Reshma, Prakash Kumar, D. Srinagesh, C. Haldar, Sanjay Kumar, Prantik Mandal, Pn tomography and anisotropic study of the Indian shield and the adjacent regions, 228932, Copyright (2021), with permission from Elsevier.)
Srinu et al. (2021) investigated the X-discontinuity beneath India,
using P-RFs at seismological stations deployed on the Indian shield and
the Himalaya. They detect the X-discontinuity as a sporadic and thin
feature in the depth range of 246–335 km, with a sharp shear velocity
jump of 2.5-3.6%.
The DVP is considered to have its genesis in the interaction of the
Indian plate with the Réunion mantle plume. Sharma J., et al. (2021)
investigated the group velocity dispersion data in the period range of
6-100 s derived from waveforms of 77 regional earthquakes recorded at 38
broadband stations and performed surface wave tomography. The results
revealed signatures of magmatic underplating and a thick crust beneath
the Kachchh seismic zone and Western Ghats. A predominant low-velocity
zone beneath the Cambay, Saurashtra, and adjoining regions was
interpreted as a residual thermal anomaly and thin lithosphere as a
result of weakening due to plume-lithosphere interaction.
Singh and Singh (2019) presented a high-resolution seismic image of the
hitherto-elusive crustal architecture of the Eastern Ghat Mobile Belt
(EGMB) and its contact with Archaean cratons using teleseismic receiver
functions. The results reveal a thick crust (40 km) with oppositely
dipping Moho below the contact between the EGMB and the Bastar craton.
The crust of Bastar craton extends ( \(\sim\) 75 km) eastward
beneath the EGMB-Bastar surficial contact. Jana et al. (2022)
constrained the velocity model by jointly inverting the surface wave
dispersion data with receiver function data (Fig.2). The lithospheric
and asthenospheric velocity model excludes the possibility of southward
accretionary growth of Singhbhum craton to form Rengali province. Also,
a metasomatically altered zone has been reported in some areas. The
signature of removal of lithospheric root beneath the investigating
region indicates the thermo-mechanical destruction caused by plume
hotspots during the northward drift of proto-India.
Mullick et al. (2022) obtained a 3-D shear velocity model of South
Indian Precambrian terrains at a lateral resolution of 55 km down to 250
km depth by inversion of fundamental mode Rayleigh wave phase velocity
dispersion data in the period range of 30-140s, which shows a 150-200 km
thick lithosphere beneath most of the Archaean Dharwar craton. An
extraordinary high shear velocity (up to 4.8 km/s) and thick lithosphere
(150 km) are observed beneath the Proterozoic Carbonatite complex,
located at the south-eastern edge of the Dharwar craton. They inferred a
compositional modification of the lower lithosphere at the south-western
margin of the Dharwar craton and lithospheric erosion in the Granulite
terrain both possibly due to interaction with the Marion mantle plume at
\(\sim\) 90 Ma.