Thrust Fault

Thrust Fault a common type of fault in which hanging wall moves upward in relation to footwall. In Bangladesh thrust faults are usually associated with the anticlines of the eastern fold belts. The eastern fold belt of the Chittagong-Tripura, known widely as the frontal fold belt of the Indo-Burman range has its origin in the subduction of the Indian plate beneath the Burmese plate.

The major anticlines of the fold thrust belts are accompanied by the thrust faults either in one both the limbs. The thrust faults are east dipping. For example, most of the major anticlines of the Chittagong fold belts (anticlines at Sitapahar, Sitakund, Bandarban, Gobamura, Matamuhuri, Dakkhin Nhila, Uthanchatra) have major east dipping thrust faults on the western limb while some of them also have thrust fault (west dipping) in the eastern limb. The intensity of the thrust faults increases to the east and decreases towards west. In the western part of the fold belt, the intensity of folding is decreased and the folds are not associated with major thrust fault. Where the fold belt merges with the foredeep further west, the anticlines are simple, gentle, and are not faulted.

The thrust faults are oriented along NW-SE direction conforming to the strike of the anticlines. Satellite images show that there are some cross faults also within the fold belts, which cut across the anticlines. This is also evidenced from sudden straightening of river courses.

Thrust faults have significant effect on the topography and disposition of stratigraphic units in the Chittagong fold belts. Major escarpments i.e., steep reliefs on the west side of anticlines are the results of thrust faults. These also bring the very young formation in juxtaposition to old formation. For example, the Tipam formation is juxtaposed against Bhuban Formation. [Sifatul Quader Chowdhury]

See also fault.

See map in fault.