Two distinct shear wave splitting directions in the northwestern Deccan Volcanic Province

Rao, K.; Kumar, M. Ravi; Singh, Arun; Rastogi, B. K.

doi:10.1002/2013jb010644

Cited by 23 publications

(7 citation statements)

References 43 publications

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“…In the right panel the differences are plotted at particular node points, where color and symbol both represents the difference in the depth estimates. Kumar et al, 2013Zhang et al, 2012Xu et al, 2011Uma et al, 2009Kumar et al, 2007Kumar et al, 2005 100 Kumar et al, 2013Kosarev et al, 2013Oreshin et al, 2008Kayal et al, 2011Singh et al, 2009Kislev et al, 2008Shen et al, 2008Pathak et al, 2006Kosarev et al, 1999Yuan et al, 1999 Singh and Kumar (2009); Kiselev et al (2008); Shen et al (2008); Pathak et al (2006); Kosarev et al (1999); Yuan et al (1997). Different symbols are used to indicate each set of results.…”

Section: Discussionmentioning

confidence: 99%

A review of crust and upper mantle structure beneath the Indian subcontinent

Singh

Kennett

2015

Tectonophysics

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This review presents an account of the variations in crustal and upper mantle structure beneath the Indian subcontinent and its environs, with emphasis on passive seismic results supplemented by results using controlled seismic sources. Receiver function results from more than 600 seismic stations, and over 10,000 km of deep seismic profiles have been exploited to produce maps of average crustal velocities and thickness across the region. The crustal thickness varies from 29 km at the southern tip of India to 88 km under the Himalayan collision zone, and the patterns of variation show significant deviations from the predictions of global models. The average crustal shear velocity (Vs) is low in the Himalaya-Tibet collision zone compared to Indian shield. Major crustal features are: (a) the Eastern Dharwar Craton has a thinner and simpler crustal structure crust than the Western Dharwar Craton, (b) Himalayan crustal thickness picks clearly follow a trend with elevation, (c) The rift zones of the Godavari graben and Narmada-Son lineament show deeper depths of crust than their surroundings, and (d) most of the Indian cratonic fragments, Bundelkhand, Bhandara and Singhbhum, show thick crust in comparison to the Eastern Dharwar Craton. Heat flow and crustal thickness estimates do not show any positive correlations for India. Estimates of the thickness of the lithosphere show large inconsistencies among various techniques not only in terms of thickness but also in the nature of the transition to the asthenosphere (gradual or sharp). The lithosphere beneath India show signs of attrition and preservation in different regions, with a highly heterogeneous nature, and does not appear to have been thinned on broader scale during India's rapid motion north towards 1 Asia. The mantle transition zone beneath India is predominantly normal with some clear variations in the Himalayan region (early arrivals) and Southwest Deccan Volcanic Province and Southern Granulite Terrain (delayed arrivals). No clear patterns on influence on the mantle transition zone discontinuities can be associated with lithospheric thickness. Over 1000 anisotropic splitting parameters from SKS/SKKS phases and 231 using direct S waves are available from various studies. The shear-wave splitting results clearly show the dominance of absolute-plate-motion related strain of a highly anisotropic Indian lithospheric mantle with delay times between the split S phases close to 1 s. There are still many parts of India where there is, at best, limited information on the character of the crust and the mantle beneath. It is to be hoped that further installations of permanent and temporary stations will fill these gaps and improve understanding of the geodynamic environment of the Indian subcontinent.

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Section: Discussionmentioning

confidence: 99%

A review of crust and upper mantle structure beneath the Indian subcontinent

Singh

Kennett

2015

Tectonophysics

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“…The shear wave splitting parameters required for correcting the P wave travel times are compiled from the published measurements from India [Singh et al, 2006Kumar and Singh, 2008;Oreshin et al, 2008;Heintz et al, 2009;Mandal, 2011;Roy et al, 2012;Rao et al, 2013;Hazarika et al, 2013]. For parts of Himalaya and Tibet, we used the splitting parameters from the global database [W€ ustefeld et al, 2008].…”

Section: Sks Splitting Data Setmentioning

confidence: 99%

“…It incorporates corrections using SKS splitting parameters (i.e., azimuthal anisotropy), which are sensitive to horizontal fast-axis alignment, but do not account for the effects of radial anisotropy. For a given ray, the P wave correction time t p due to assumed anisotropy in the upper mantle is given by [Singh et al, 2006Kumar and Singh, 2008;Oreshin et al, 2008;Heintz et al, 2009;Mandal, 2011;Roy et al, 2012;Rao et al, 2013;Hazarika et al, 2013]. The splitting results from Tibet are basically from the compilations of W€ ustefeld et al Geochemistry, Geophysics, Geosystems 10.1002/2015GC006064 t p 5dt s ½ðV P anis 21 2V P iso 21 Þ=ðV S fast 21 2V S slow 21 Þ…”

Section: Time Corrections To Teleseismic P Wavesmentioning

confidence: 99%

P wave velocity structure below India and Tibet incorporating anisotropic delay time effects

Mohanty

Singh

O'Driscoll

et al. 2016

Geochem Geophys Geosyst

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We incorporate the effects of anisotropy to refine the continental‐scale 3‐D isotropic velocity model previously produced for India and Tibet by inverting 52,050 teleseismic P wave residuals. We have exploited a total of 1648 individual SKS splitting parameters to calculate the P wave travel time corrections due to azimuthal anisotropy. Our results suggest that anisotropy affects the P wave delays significantly (−0.3 to +0.5 s). Integration of these corrections into the 3‐D modeling is achieved in two ways: (a) a priori adjustment to the delay time vector and (b) inverting only for anisotropic delays by introducing strong damping above 80 km and below 360 km depths and then subtracting the obtained anisotropic artifact image from the isotropic image, to get the corrected image. Under the assumption of azimuthal anisotropy resulting from lattice preferred orientation (LPO) alignment due to horizontal flow, the bias in isotropic P wave tomographic images is clear. The anisotropy corrected velocity perturbations are in the range of ±1.2% at depths of around 150 km and reduced further at deeper levels. Although the bias due to anisotropy does not affect the gross features, it does introduce certain artifacts at deeper levels.

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“…Seismic anisotropy is an integral effect of various causatives; crustal anisotropy due to fractures in shear zones and melts, frozen anisotropy due to strain accumulation in the lithospheric material from past tectonic and deformation processes, anisotropy due to lattice preferred orientation (LPO) in response to asthenospheric flow (e.g., Rao et al, 2013;Romanowicz & Wenk, 2017;Yuan et al, 2011). Azimuthal (using SKS/SKKS phases) and radial (using Surface waves) anisotropy are mainly used to decipher the geodynamic changes beneath continental and oceanic regions.…”

Section: Introductionmentioning

confidence: 99%

“…Globally, many studies have attempted to characterize the anisotropic structure using surface waves (e.g., Debayle & Sambridge, 2004;Kustowski et al, 2008a;Montagner, 2007;Romanowicz & Wenk, 2017). However, few studies are performed to understand seismic anisotropy beneath the DVP (e.g., Prajapati et al, 2011;Rao et al, 2013). The one-dimensional (1-D) crustal structure across the Gulf of Cambay estimated using sparse surface wave datasets reveals a large positive radial anisotropy in the Deccan Traps and upper crust (12-14 %) (Prajapati et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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Two distinct shear wave splitting directions in the northwestern Deccan Volcanic Province

Cited by 23 publications

References 43 publications

A review of crust and upper mantle structure beneath the Indian subcontinent

A review of crust and upper mantle structure beneath the Indian subcontinent

P wave velocity structure below India and Tibet incorporating anisotropic delay time effects

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

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