Scarps Generated by Erosion and Sedimentation

Abstract

The Ganges–Brahmaputra Delta (GBD), the world’s largest delta, is composed of sediments eroded from the collision zone of Himalayas. These sediments moved the margin of the Indian Subcontinent for ~400 km and formed the thickest sedimentary sequence, which is subducted within the subduction zone of the Burma arc. A critical facility is located in the GBD central part. Although it is located for more than 300 km from the Indo-Burma subduction zone in the east and the continental collision zone in the north, these planetary structures significantly affects the seismic activity and seismic hazard of the GBD central part. Scarps exposed by trenches in the vicinities of this object were found in the surface and studied. The trench walls exhibit inclined layers with small vertical displacement, which could indicate a former paleoearthquake, however, they are underlain by horizontal layers without displacement. This pattern is interpreted as a result of erosion (neotectonic) activity related to repeated fluctuations of the Ganges River bed, which are traced in all trenches.