Crustal structure beneath northeast India inferred from receiver function modeling

Borah, Kajaljyoti; Bora, Dipok K.; Goyal, Ayush; Kumar, Rajan

doi:10.1016/j.pepi.2016.07.005

Cited by 23 publications

(22 citation statements)

References 44 publications

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“…Moho depth is observed between ∼30 and 32 km beneath the MH. Borah et al (2016) obtained crustal thickness of 32-36 km north of SM based on the S-wave velocity model. The occurrence of thinned crust (30-32 km) beneath SM is also reported by Mitra et al (2018) and Priestley et al (2019).…”

Section: Shear Wave Velocity Structurementioning

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 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: Shear Wave Velocity Structurementioning

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 average elevation of the Shillong Plateau is ∼1 km and is associated with positive gravity anomaly (Verma & Mukhopadhyay, 1977), indicating the lack of a significant crustal root. Receiver function studies (Bora et al, 2014;Borah et al, 2016;Mitra et al, 2005;Ramesh et al, 2005) have confirmed that the crust beneath the Shillong Plateau is indeed the thinnest in NE India and increases both to the north and south of the plateau. These suggest a model of tectonic support of the plateau in the form of crustal scale bounding reverse faults, namely the north dipping Dawki Fault to the south and the blind south dipping Oldham Fault to the north (Bilham & England, 2001).…”

Section: Introductionmentioning

confidence: 95%

“…To the east, the plateau is separated from the Mikir Hills by the buried dextral strike-slip Kopili Fault Zone (KFZ) (Vernant et al, 2014), which has hosted a number of recent moderate earthquakes (Kumar et al, 2015). Receiver function studies (Bora et al, 2014;Borah et al, 2016;Mitra et al, 2005;Ramesh et al, 2005) have confirmed that the crust beneath the Shillong Plateau is indeed the thinnest in NE India and increases both to the north and south of the plateau. Receiver function studies (Bora et al, 2014;Borah et al, 2016;Mitra et al, 2005;Ramesh et al, 2005) have confirmed that the crust beneath the Shillong Plateau is indeed the thinnest in NE India and increases both to the north and south of the plateau.…”

Section: Introductionmentioning

confidence: 99%

Crustal Structure and Evolution of the Eastern Himalayan Plate Boundary System, Northeast India

et al. 2018

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We use data from 24 broadband seismographs located south of the Eastern Himalayan plate boundary system to investigate the crustal structure beneath Northeast India. P wave receiver function analysis reveals felsic continental crust beneath the Brahmaputra Valley, Shillong Plateau and Mikir Hills, and mafic thinned passive margin transitional crust (basement layer) beneath the Bengal Basin. Within the continental crust, the central Shillong Plateau and Mikir Hills have the thinnest crust (30 ± 2 km) with similar velocity structure, suggesting a unified origin and uplift history. North of the plateau and Mikir Hills the crustal thickness increases sharply by 8–10 km and is modeled by ∼30∘ north dipping Moho flexure. South of the plateau, across the ∼1 km topographic relief of the Dawki Fault, the crustal thickness increases abruptly by 12–13 km and is modeled by downfaulting of the plateau crust, overlain by 13–14 km thick sedimentary layer/rocks of the Bengal Basin. Farther south, beneath central Bengal Basin, the basement layer is thinner (20–22 km) and has higher Vs (∼4.1 km s−1) indicating a transitional crystalline crust, overlain by the thickest sedimentary layer/rocks (18–20 km). Our models suggest that the uplift of the Shillong Plateau occurred by thrust faulting on the reactivated Dawki Fault, a continent margin paleorift fault, and subsequent back thrusting on the south dipping Oldham Fault, in response to flexural loading of the Eastern Himalaya. Our estimated Dawki Fault offset combined with timing of surface uplift of the plateau reveals a reasonable match between long‐term uplift and convergence rate across the Dawki Fault with present‐day GPS velocities.

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“…This requires well‐constrained velocity structure to enable precise location of earthquakes, computation of earthquake source properties to characterize the source zones, and estimation of seismic wave attenuation from the source to any point on the surface of the Earth. The first two have been extensively studied for northeast India, over the past decade (Bora et al, ; Borah et al, ; Kumar et al, ; Mitra et al, ; Mitra et al, ; Ramesh et al, ), but gaps exist in our knowledge of the attenuation structure. The present study focuses on estimation of seismic wave attenuation at a range of frequencies to ascertain the quality factor ( Q ) and its frequency dependence ( η ) for the crust beneath northeast India.…”

Section: Introductionmentioning

confidence: 99%

Seismic Attenuation of the Eastern Himalayan and Indo‐Burman Plate Boundary Systems, Northeast India

Sharma

Mitra

2018

JGR Solid Earth

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We use local earthquake coda waveform to characterize the seismic attenuation across northeast India. We measure temporal decay of coda amplitude to estimate coda quality factor (Qc) at frequencies 1 to 14 Hz and abstract Q0 and its frequency dependence (η). Single‐trace measurements reveal similar average Qc between 1 and 3 Hz and significant variation at higher frequencies. We combine single‐trace Qc measurements into a backprojection algorithm to compute 2‐D Qc tomography maps. The Qc maps reveal strong correlation with tectonic settings. At low frequencies (1–5 Hz) we observe relatively lower Qc in the Sikkim and Eastern Himalaya, southern Tibetan Plateau, and Bengal Basin, while the intraplate region and Indo‐Burman subduction zone have higher Qc. At higher frequencies (>5 Hz) we observe pronounced low Qc beneath Sikkim Himalaya, relatively lower Qc in the intraplate region and relatively higher Qc in the Bengal Basin and Indo‐Burman subduction zone. We compare our Q0 map with Vs tomography to characterize the crust. The lateral variation in the structure of the Himalayan thrust sheets between Sikkim and Eastern Himalaya is highlighted by low and intermediate Q0, respectively. The southern Tibetan Plateau, known to have low Vs due to elevated crustal temperatures, is characterized by low Q0, indicating associated scattering and anelastic effects. The intraplate continental crust and the cold elastic subducting oceanic lithosphere have intermediate‐to‐high Vs and are marked by high Q0. The Bengal Basin, with thick low Vs sedimentary layers overlying a rift‐faulted high Vs transitional crust, has low‐to‐intermediate Q0 due to depth averaging of attenuation characteristics.

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Crustal structure beneath northeast India inferred from receiver function modeling

Cited by 23 publications

References 44 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

Crustal Structure and Evolution of the Eastern Himalayan Plate Boundary System, Northeast India

Seismic Attenuation of the Eastern Himalayan and Indo‐Burman Plate Boundary Systems, Northeast India

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