Lateral variation in crustal and mantle structure in Bay of Bengal based on surface wave data

Kumar, Amit; Mukhopadhyay, S.; Kumar, Naresh; Baidya, P. R.

doi:10.1016/j.jog.2017.11.006

Cited by 11 publications

(7 citation statements)

References 43 publications

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“…A higher velocity gradient in the western part of the BB relative to the eastern part of it shows that the basement depth increases from west to east. Low group velocity (from 4 s to 16 s) in BRV and IGP is also evidence of the presence of sediment at shallow depth (Kumar et al, 2018a). Kayal (2008) reported that the average sediment thickness in BRV is ∼4 km.…”

Section: Tomographic Imagesmentioning

confidence: 95%

“…Based on paleomagnetic, gravity, and deep seismic sounding data, Talwani et al (2016) too found the zone of transition from oceanic to continental crust near this area. Brune and Singh (1986) and Kumar et al (2018a) found that average Vs in BB changes from oceanic type in its southern part to more continental type toward the north. Based on previous works using Rayleigh wave close to this study region (Acton et al, 2010;Bora et al, 2014;Kumar et al, 2019), 4.0 km/s contour is taken as the Moho discontinuity.…”

Section: Bay Of Bengal and Indo-burma Rangementioning

confidence: 99%

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Tomographic Image of Shear Wave Structure of NE India Based on Analysis of Rayleigh Wave Data

Kumar

Mukhopadhyay

et al. 2021

Front. Earth Sci.

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The major scientific purpose of this work is to evaluate the geodynamic processes involved in the development of tectonic features of NE India and its surroundings. In this work, we have obtained tomographic images of the crust and uppermost mantle using inversion of Rayleigh waveform data to augment information about the subsurface gleaned by previous works. The images obtained reveal a very complicated tectonic regime. The Bengal Basin comprises a thick layer of sediments with the thickness increasing from west to east and a sudden steepening of the basement on the eastern side of the Eocene Hinge zone. The nature of the crust below the Bengal Basin varies from oceanic in the south to continental in the north. Indo-Gangetic and Brahmaputra River Valleys comprise ∼5–6-km-thick sediments. Crustal thickness in the higher Himalayas and southern Tibet is ∼70 km but varies between ∼30 and ∼40 km in the remaining part. Several patches of low-velocity medium present in the mid-to-lower crust of southern Tibet along and across the major rifts indicate the presence of either partially molten materials or aqueous fluid. Moho depth decreases drastically from west to east across the Yadong-Gulu rift indicating the complex effect of underthrusting of the Indian plate below the Eurasian plate. Crust and upper mantle below the Shillong Massif and Mikir Hills are at a shallow level. This observation indicates that tectonic forces contribute to the uprising of the Massif.

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Section: Tomographic Imagesmentioning

confidence: 95%

Section: Bay Of Bengal and Indo-burma Rangementioning

confidence: 99%

Tomographic Image of Shear Wave Structure of NE India Based on Analysis of Rayleigh Wave Data

Kumar

Mukhopadhyay

et al. 2021

Front. Earth Sci.

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“…The joint study of multichannel seismic reflection, gravity, magnetic, and bathymetric data in the Bay of Bengal south of 18°N implies that the oceanic crust of the Indian Plate is steeply subducting beneath the Burma microplate 20 . The shear wave velocity structure beneath the Bay of Bengal estimated from the surface wave data indicate that the crustal thickness increases from south to north and that the crustal velocity decreases from a higher oceanic crust-like value at the southern end to a lower continental crust-like value at the northern end 21 .…”

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confidence: 98%

Direct structural evidence of Indian continental subduction beneath Myanmar

Zheng

Ding

et al. 2020

Nat Commun

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Indian continental subduction can explain Cenozoic crustal deformation, magmatic activity and uplift of the Tibetan Plateau following the India-Asia collision. In the western Himalayan syntaxis and central Himalaya, subduction or underthrusting of the Indian Plate beneath the Eurasian Plate is well known from seismological studies. However, because information on the deep structure of the eastern Himalayan syntaxis is lacking, the nature of the Indian subduction slab beneath Myanmar and the related tectonic regime remain unclear. Here, we use receiver function common conversion point imaging from a densely spaced seismic array to detect direct structural evidence of present-day Indian continental subduction beneath Asia. The entire subducting Indian crust has an average crustal thickness of~30 km, dips at an angle of~19°, and extends to a depth of 100 km under central Myanmar. These results reveal a unique continental subduction regime as a result of Indian-Eurasian continental collision and lateral extrusion.

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“…The stations located over or close to the Tripura Fold Belt (AZL, BEL, and AGT) show a high Poisson's ratio (σ ≥ 0.277) except for one station SAIH that shows σ~0.245. The Tripura Fold Thrust Belt (part of IBR) can be interpreted as an accretionary wedge which is mainly composed of folded sequence marine/flysch sedimentary rocks (shale, limestone, and sandstone) at the top, along with high‐velocity basaltic rocks of oceanic crust origin at the basement (Kumar, Mukhopadhyay, Kumar, & Baidya, 2018; Mitra, Bhattacharyya, & Nath, 2008; Rahman et al, 2020). The clay minerals present in the sedimentary rocks along with the presence of mafic rocks (basalt) at the basement cause the high Poisson's ratio in the Tripura Fold Thrust Belt.…”

Section: Resultsmentioning

confidence: 99%

Spatial variations of crustal thickness and Poisson's ratio in the northeastern region of India based on receiver function analysis

et al. 2022

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Crustal configuration beneath the northeastern region of India has been investigated with the help of receiver function (RF) analysis of teleseismic earthquakes recorded by 19 broadband seismological stations. We adopted the H‐k stacking method to estimate crustal thickness and Poisson's ratio beneath each recording station. The study reveals a large variation in crustal thickness and Poisson's ratio which are correlated with the complex geology and tectonics of the region. The crust is observed to be thinner (36.5–41.6 km) beneath Bengal Basin, Shillong Plateau, and the Brahmaputra valley compared to the Indo‐Burma Ranges (IBR) (~40–54 km) and Arunachal Higher Himalaya (TAWA station, ~45 km) and Sikkim Himalaya (GTK station, ~46.5 km). A large variation of Poisson's ratio is observed in the region (~0.230–0.306). Poisson's ratio is generally low‐to‐intermediate in the Shillong‐Mikir Plateau, Bengal Basin, and the Brahmaputra Valley, while it is intermediate‐to‐high in the Tripura Fold Belt and the northern part of the IBR. The high Poisson's ratio in the Tripura Fold Belt is due to the presence of basaltic basement rock and clay minerals existing in the sedimentary rocks, whereas the presence of partially serpentinized rock in the ophiolitic mélange complex causes a high Poisson's ratio in the IBR.

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Lateral variation in crustal and mantle structure in Bay of Bengal based on surface wave data

Cited by 11 publications

References 43 publications

Tomographic Image of Shear Wave Structure of NE India Based on Analysis of Rayleigh Wave Data

Tomographic Image of Shear Wave Structure of NE India Based on Analysis of Rayleigh Wave Data

Direct structural evidence of Indian continental subduction beneath Myanmar

Spatial variations of crustal thickness and Poisson's ratio in the northeastern region of India based on receiver function analysis

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