Seismotectonic significance of the December 1, 2020 Haridwar, India earthquake (M 4.3), a lower crust event near the Himalayan topographic front

High-quality data recorded by a dense network of 53 seismic stations in the Garhwal–Kumaun Himalaya between February 2017 and December 2021 is analyzed. A total of 813 local earthquakes are relocated using a newly developed regional 1D velocity model incorporating station corrections. In addition, focal mechanism solutions of M ≥ 3.8 events are estimated using waveform inversion. The relocated seismicity patterns along with the focal mechanism solutions are utilized to present a seismotectonic scenario of the region. Almost 95% of the relocated seismicity is found to be clustered along the Himalayan seismic belt (HSB), down to ∼24 km depth. Seismicity in this belt is interpreted to be caused due to interseismic stress loading associated with the ongoing India–Eurasia collision tectonics. A few scattered hypocenters in the deeper crust between 30 and 50 km depth attest the strength of the downgoing Indian plate. Focal mechanisms in the seismogenic upper crust reveal thrusting of the Indian plate beneath the Lesser Himalaya, with compression normal to the strike of the Main Central Thrust (MCT). The north-dipping thrust mechanisms can be associated with a near-horizontal Main Himalayan Thrust (MHT). In addition, more steeply dipping faults above it define the Lesser Himalayan duplex systems, similar to those in western and Nepal Himalaya. A prominent ∼50 km wide seismicity gap region observed within the HSB is probably due to (1) a locally varying locking width of the MHT; (2) an unruptured, ductile segment at the eastern end of the rupture zone of the great 1803 earthquake (Mw 7.8 ± 0.2); and (3) a slab tear in the MHT, similar to those in subduction zones.

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Evidence of northward dipping crustal layers underneath the eastern part of the Indo- Gangetic foreland basin, India: Implication for geodynamic evolution and seismogenesis

Chouhan,

Kumar,

Islam

et al. 2024

Preprint

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The continual collision and convergence of two plates, the Indian and the Eurasian plates, of extensively different crustal thicknesses, created one of the most dynamic geological provinces in the northern part of the Indian subcontinent, the Indo-Gangetic foreland basin (IGFB). The crustal geometry in this part of the Indian plate has remained the prime focus of many researchers due to the occurrence of devastating earthquakes. In this context, we complement previous works and aim to map the crustal layers to make a realistic and most acceptable premise for tectonogenesis of the eastern IGFB. The derivative analysis of the Bouguer anomaly delineates the east-west trending basement-controlled subsurface geological structures related to the Miocene and Pleistocene epochs. The results of our study inferred that the Precambrian basement and Moho depth varies between 1 to 6.8 km and 39 to 60 km, respectively. The forward modelling of the Bouguer anomaly reveals that the crustal interfaces beneath the eastern IGFB are sharply dipping toward the north direction, primarily associated with the Himalayan orogeny of the Miocene and Pleistocene epochs. The findings of this study suggest that the Munger-Saharsa ridge controls subsidence in this part of the IGFB from the Miocene epoch to the present. Moreover, the study has also identified a blind fault in the Gandak depression, and its rapport with seismicity in the region is discussed. We have argued that the Munger-Saharsa ridge and the crustal bending mainly influence the seismicity in the eastern part of the IGFB.

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Seismotectonic significance of the December 1, 2020 Haridwar, India earthquake (M 4.3), a lower crust event near the Himalayan topographic front

Cited by 3 publications

References 42 publications

Exploring the Link Between Seismic and Atmospheric Parameters Using Spatio Temporal Analysis: Implications for Earthquake Forecasting

Exploring the Link Between Seismic and Atmospheric Parameters Using Spatio Temporal Analysis: Implications for Earthquake Forecasting

Nature of the Himalayan Seismicity Belt in the Garhwal–Kumaun Segment and Its Tectonic Implications

Evidence of northward dipping crustal layers underneath the eastern part of the Indo- Gangetic foreland basin, India: Implication for geodynamic evolution and seismogenesis

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