T31C-4636:
Tectonics of Modhupur Tract, its Effects on the Cenozoic Sediments and Jamuna River Avulsion

Wednesday, 17 December 2014
Alamgir Hosain, University of Dhaka, Dhaka, Bangladesh
Abstract:
Bangladesh is a country characterized by numerous natural disasters. These natural hazards occur both on the surface (e.g., flooding due to river avulsions) and within the subsurface (e.g., earthquakes) (see figure), and both types have been related to regional tectonic activity. Bangladesh is also one of the most highly populated countries in the world with a capital city, Dhaka, host to 17 million people. This urban center is located only 40 km south east from the Madhupur Tract, a potentially tectonically hazardous region. In order to determine this region’s tectonic hazard potential, recent studies have attempted to detect and identify significant neotectonic signatures of the tract, such as faults, lineaments, and weak zones within the region. Recent earthquake evidence along the Madhupur Fault strongly supports the fact that the area is tectonically unstable and quite vulnerable to further seismicity, placing the fast-growing and densely populated Dhaka city in potential danger (see figure).

The Madhupur Tract is in central Bangladesh, and is surrounded by the Jamuna-Brahmaputra river floodplain. Previous research suggests the uplift of the Madhupur Tract may have exerted a significant control on the avulsion history of the Jamuna River. The Jamuna river avulsion history is cyclic, with a periodicity of about 2000 years. Within these cycles, the Jamuna’s position has fluctuated from west to east and east to west, repeatedly (Pickering et al. 2013). As this avulsion history is thought to be, at least partly, related to seismicity in the region, future seismicity has the potential to cause future river avulsions and related flooding.

The Madhupur Tract is an exposed Quaternary deposit. It is believed that 1885 Bengal earthquake may have been caused by the rupture of the Madhupur blind fault (see figure). However, there is no paleo-seismological evidence, since it is an intra-plate active fault.

The principle aim of this research is to identify the location of the Madhupur fault and determine the connection between activity along the fault and the avulsion history of the Jamuna River. To this end, we aim to determine, more precisely, the intensity of the fault, the local lithology using resistivity survey data, and ultimately the exact cause of Jamuna River avulsion.