Seismic velocity imaging of the Kumaon–Garhwal Himalaya, India

Mandal, Prantik; Srinagesh, D.; Vijayaraghavan, R.; Suresh, G.; Naresh, B.; Raju, P. V. Sunder; Devi, Aarti; Swathi, K.; Singh, Dinesh; Srinivas, D.; Saha, Sankhadip; Shekar, M.; Sarma, A. N. S.; Murthy, Y. V. V. B. S. N.

doi:10.1007/s11069-021-05135-4

Cited by 13 publications

(16 citation statements)

References 35 publications

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“…Surprisingly, the vertical downward projections of the hypocenters of the Uttarkashi (UK) earthquake in 1991 and the Chamoli (CH) earthquake in 1999 are both located within this zone. Thus, the 1991 M w 6.6 UK and 1999 M w 6.4 CH MHT thrust earthquakes could be linked to increased pore-fluid pressure due to the presence of metamorphic fluids at mid-crustal depths 5 , 33 , 46 . Furthermore, the major variations in Moho depths (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The use of Rayleigh wave group velocity dispersion data up to 100 s has enabled us to delineate the V s -structure up to a depth of 200 km 45 . Here, the crustal part of initial 1-D velocity models are constrained by the final Vp and Vs models as obtained from the simultaneous www.nature.com/scientificreports/ inversion of P-and S-arrival times 46 while the deeper part of initial velocity models are constrained by the IASP91 model of Kennett and Engdahl 47 . The Moho depths for the initial models are varying from 28.3 km (at BTL) to 52.9 km (at PAUR) 5 .…”

Section: Joint Inversion Of Prfs and Surface Wave Group Velocity Disp...mentioning

confidence: 99%

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Evidence of structural segmentation of the Uttarakhand Himalaya and its implications for earthquake hazard

Mandal

Prathigadapa

Srinivas

et al. 2023

Sci Rep

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The earthquake hazard associated with the Main Himalayan Thrust (MHT) is a critical issue for India and its neighbouring countries in the north. We used data from a dense seismic network in Uttarakhand, India, to model the lateral variations in the depths of MHT (2–6% drop in Vs at 12–21 km depths), Moho (a sharp increase in Vs (by ~ 0.5–0.7 km/s) at 39–50 km depths) and lithosphere (a marked decrease in Vs(~ 1–3%) at 136–178 km depths), across the Himalayan collisional front. Our joint inversion of radial PRFs and group velocity dispersion data of Rayleigh waves detects three NNE trending transverse lithospheric blocks segmenting the lithosphere in Uttarakhand Himalaya, which spatially correlate well with the northward extension of the Delhi -Haridwar Indian basement ridge, an inferred tectonic boundary and great boundary fault, respectively. Our radial receiver function imaging detects highly deformed and segmented crustal and lithospheric structures associated with three mapped transverse lithospheric blocks, suggesting a reduction in rupture lengths of future earthquakes, thereby, reducing earthquake hazards in Uttarakhand.

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Section: Resultsmentioning

confidence: 99%

Section: Joint Inversion Of Prfs and Surface Wave Group Velocity Disp...mentioning

confidence: 99%

Evidence of structural segmentation of the Uttarakhand Himalaya and its implications for earthquake hazard

Mandal

Prathigadapa

Srinivas

et al. 2023

Sci Rep

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“…They also mapped three NNE-SSW trending transverse crustal blocks in Uttarakhand Himalaya that extend down to the lithosphere-asthenosphere boundary. Local earthquake tomography of the Kumaun-Garhwal Himalaya (Mandal et al, 2022b;Gupta S., et al, 2022) shows a low velocity (Vp, Vs), high Vp/Vs mid-crustal layer, which was identified as the Main Himalayan Thrust associated with metamorphic fluid/partial melt.…”

Section: Himalayamentioning

confidence: 99%

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

Manglik

2023

Preprint

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The Indian National Science Academy (INSA), the National Adhering body representing India in the International Union of Geodesy and Geophysics (IUGG), submits a National Report to the IUGG during its General Assembly, held every four years. The present chapter is a compilation for the International Association of Seismology and Physics of the Earth's Interior (IASPEI), one of the eight Associations of the IUGG, encompassing the scientific activities carried out in the country during 2019-2022, in the field of seismology. The chapter is arranged to categorize the contributions under internal structure of the Indian lithosphere and sub-lithospheric mantle, crust and upper mantle deformation, seismic attenuation, seismic hazards, triggered seismicity, environmental seismology, paleoseismology and seismological networks. In addition, the chapter includes activities related to societal projects and outreach programs. It is not an exhaustive review of the entire Indian contribution to seismology and allied fields during this period but a window to the topics covered within the framework of IASPEI.During the reporting period, researchers from several Indian R&D and Academic Institutions continued adding new results on the crustal and upper mantle structure of the Indian shield, both at regional and geological province scale. The Himalaya has been a major focus of seismological research for many Institutes who operated broadband seismological networks from Kashmir to Arunachal along the Himalayan arc. The data from these networks have facilitated in enhancing our understanding of the structure of the Main Himalayan Thrust, crustal and upper mantle structure as well as the dip of the underthrusting Indian plate, seismicity monitoring, and estimation of attenuation. Some of these networks also include accelerographs for strong ground motion studies. A few studies also focused on mapping of the mantle transition zone beneath the Indian Ocean Geoid Low. The studies on anthropogenic seismicity added near-field investigations in the Koyna -Warna region through borehole seismology. Organization of the Joint Scientific Assembly of IAGA and IASPEI during 21-27 August 2021 (JSA-2021) was a major event during this period related to the IUGG activities. Originally, the event was planned to be hosted at Hyderabad, India, but due to the COVID-19 pandemic it was organized in virtual mode. Initiatives have been taken to nucleate the field of environmental seismology in the country.

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“…Three-dimensional P-and S-velocity structure has been modelled by Mandal et al 25 , through a seismic velocity tomographic method developed by Benz et al 26 and subsequently modi ed by Pujol and Shen 27 .…”

Section: Three-dimensional Velocity Inversionmentioning

confidence: 99%

“…Checkerboard, as well as synthetic tests, suggest that 80-90% of the assumed velocity anomaly can be retrieved for the aftershock zone, whereas, only 70-80% for the surrounding regions . The details of the results of checkerboard as well as synthetic tests can be found in Mandal et al 25 . Here, we present depth-cross-sections of Vp, Vs and Vp/Vs tomograms along with two NE-SW (i.e.…”

Section: Three-dimensional Velocity Inversionmentioning

confidence: 99%

Marked lateral variations in the Moho topography below the Uttarakhand Himalaya (India)

Mandal

Prathigadapa

Saha

2022

Preprint

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Utilizing broadband waveform data from 52 stations, we model the detailed crustal structure below the Uttrakhand Himalaya through the Common Conversion Point (CCP) staking of radial P- receiver functions and seismic velocity tomography. We detect marked lateral variations in the Moho depths dipping toward the east (i.e. perpendicular to the direction of the Indian plate motion), supporting the idea that deformations in the lower crust have been decoupled from the Upper Mantle below. We also model some double Moho structures across and along the strike of the collisional front, which could be the imprints of the broken Moho boundary resulted from the huge impact of the Himalayan collision. We detect a mid-crustal low-velocity zone between 10 and 20 km depth (10–20% drop in Vp and Vs, and 10–15% increase in Vp/Vs, suggesting the presence of metamorphic/aqueous fluids) associated with the main Himalayan thrust (MHT), which was responsible for generating the 1803 Mw7.6 Uttrakhand, 1991 Mw6.8 Uttarkashi and 1999 Mw6.5 Chamoli earthquakes. A double Moho structure (at 35–60 km depths) is also detected below the main rupture zone of these earthquakes, which might be resulting in the accumulation of large crustal stresses to generate fluid-triggered earthquakes on the MHT.

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Seismic velocity imaging of the Kumaon–Garhwal Himalaya, India

Cited by 13 publications

References 35 publications

Evidence of structural segmentation of the Uttarakhand Himalaya and its implications for earthquake hazard

Evidence of structural segmentation of the Uttarakhand Himalaya and its implications for earthquake hazard

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

Marked lateral variations in the Moho topography below the Uttarakhand Himalaya (India)

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