Foreland Basin Geometry and Disposition of Major Thrust Faults as Proxies for Identification of Segmentation along the Himalayan Arc

Abstract

Along-arc variation in the geometry of the décollement surface at a convergent margin is one of the significant parameters to assess the likely magnitude of a major/great earthquake. It is linked to the crustal/lithospheric structure and pre-existing tectonic fabric of the underthrusting plate. For the Himalayan collision belt, segmentation of the Indian lithosphere along the arc has been suggested based on seismological and GPS studies, and by analysis of topography and Bouguer gravity anomaly data. These studies, confined to the Himalaya-Tibet region, linked major segmentation boundaries to three transverse ridges in the Ganga basin. Since the formation of the Indo-Gangetic foreland basin is also controlled by the thermomechanical properties of the underthrusting Indian plate, in the present work, we study the Himalaya-foreland basin system for possible segmentation of the Indian lithosphere. We analyse the foreland basin width vis-à-vis the disposition of major thrust faults along several profiles cutting across the Himalayan arc to test a possible correlation between these two parameters. The results suggest a major segmentation boundary along the Indo-Nepal border in addition to other previously discussed segmentations coinciding with major transverse ridges in the Ganga basin. This segmentation boundary coincides with the Great Boundary fault separating the Aravalli Delhi fold belt (ADFB) from the Vindhyan basin further south. We infer a possible role of this boundary in limiting westward propagation of the rupture front of the 1505 paleo-seismic event and seismicity of the ADFB through coupling between the Himalayan collision belt and the intraplate Indian shield region.