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

Abstract

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.