Low‐Velocity Zones and Negative Radial Anisotropy Beneath the Plume Perturbed Northwestern Deccan Volcanic Province

Abstract

The Deccan volcanic province (DVP) witnessed a massive outpouring of flood basalts of ∼2 million km3 volume, at ∼65 Ma, in less than a Myr. The volcanic eruption is concomitant with crustal extension, lithospheric thinning and magma influx beneath the major rift systems namely Cambay, Narmada, and Kutch. In this study, we investigate the anisotropic and isotropic variations within the crust and upper mantle beneath the northwestern DVP by estimating the shear wave velocity (VSV, VSH, and VSoigt) and radial anisotropy (ξoigt) models using the Surface Wave Tomography technique. A joint inversion of the regionalized Rayleigh and Love wave group velocities is performed, using the genetic algorithm approach. Our results reveal different intracrustal layers, lid, and a low‐velocity zone (LVZ). This LVZ comprises of a uniform asthenospheric low‐velocity layer (LVL) of average VSV 4.44 km/s and VSH 4.47 km/s, and another LVL below, of average VSV 4.45 km/s and VSH 4.41 km/s. Furthermore, the LVZ represents a negative anomaly with reference to different global models (AK135, STW105, PREM, and S2.9EA). A negative ξoigt is observed in the LVZ, indicating dominance of vertical flow. This could be related to presence of partials melts, volatile materials and/or a thermal anomaly. We also identified the Moho (∼34–40 km) and lithosphere‐asthenosphere boundary (∼84–123 km). The low VS values, negative ξoigt and a thin lithosphere (∼84 km) in the vicinity of Gulf of Cambay affirm the presence of a plume head beneath it, in concurrence with the hypothesis of Indian Plate‐Reunion plume interaction.

The life cycle of large igneous provinces

“…Transcrustal magma transport and storage networks that feed surface eruptions. Alternatively, active modification of the lower crust (including possible delamination in the case of the CRB) 72 and lithospheric mantle by ascending melts have been indicated by seismic constraints from receiver functions and surface wave radial anisotropy in the Deccan and CRB provinces 73,74 . Large-volume magma reservoirs are preserved as reflective, high-seismic-velocity layers with Moho-depth cumulative thicknesses of several to >10 km beneath the Deccan Traps, Siberian Traps, Emeishan Traps, OJP, Kerguelen, CRB, and High Arctic LIP [75][76][77][78][79] (fig.…”

Effect of coronavirus lockdowns on the ambient seismic noise levels in Gujarat, northwest India

“…At present, 25 broadband seismographs (BBS) are operating in a continuous mode in the seismically active zone of Kutch region (popularly called as Kutch Seismic Zone, KSZ), and 10 of these stations are located at an epicentral distance of ~ 50 km from the 2001 Bhuj earthquake (Figure S1). All stations are located in the same environmental conditions and have the same technical specifications [12][13][14] .…”

INSA National Report on Seismological Research in India: 2019 – 2022

“…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 anisotropic and isotropic variations within the crust and upper mantle beneath the NW DVP are investigated using surface waves (Sharma J., et al, 2021). Results reveal different intra-crustal layers, lid, and a low-velocity zone (LVZ).…”