Dauki fault
The Dauki fault is a major
Marking the southern margins of Shillong Plateau (which is much steeper than the northern slope at about a height of 1500
The Dauki Fault, according to Evans (1964), is a
Seismic activity
Judging by the geomorphic features of the Shillong Plateau, the gravity anomaly data, and uplifted Tertiary and Quaternary deposits on the southern foothills of the Shillong Plateau, Dauki Fault was long believed to be active during the Holocene period. It is assumed that the Dauki fault has ruptured three times in the past one thousand years.[2] The Dauki fault might be divided into four rupture segments, the western, central, eastern, and easternmost segments. The eastern and western segments ruptured in AD 840–920 and in 1548, respectively. The 1897 earthquake might have been caused by the rupture of the central segment.[6]
A trench investigation conducted across the Dauki Fault at Gabrakhari Village, on the western part of the Dauki fault, inferred the timing of seismic events dating back to A.D. 1500–1630. The seismic event during A.D. 1500–1630 may correspond with the 1548 Bengal earthquake, the first recorded large earthquake of Bangladesh. Sand dikes, which reach near the ground surface due to paleo-liquefactions, were confirmed at the trench. These sand dikes formed during the Great Assam Earthquake of 12 June 1897 (Mw ⩾ 8.0[7]) caused by the rupture of the Dauki fault.[2][6]
Geological features
A Hinge Zone of deep-seated normal faults in the basement complex coinciding with the eastern margin of the Calcutta-Mymensingh gravity high passes across the Dauki Fault to the Naga Hills region of Assam. The Hinge Zone is characterized by a series of step faults across its length. This Hinge Zone, characterized by a series of step faults across its length, is seismically active. The hypocentres of earthquake originating with this zone have depth ranges from 71 km to 150 km. The Zone is conventionally thought of as representing the dividing line between the Indian Platform with full thickness of continental crust and the Bengal Foredeep.[3]
In the south, north–south-trending axial surfaces of folds in Surma basin bend towards northeast while approaching the trace of Dauki fault, indicating dextral strike slip movement along the Dauki fault. This inference is further supported by the outcrop pattern of Haflong thrust in the footwall block with the concavity facing west. This thrust belonging to the BoS abruptly terminates against the younger Dauki fault. In the west, the hanging wall block of Dauki fault meets the non-folded, undeformed, near horizontal sedimentaries of Sylhet trough of Neogene. It is proposed that the Sylhet sediments were deposited in a pull-apart basin in the releasing bend of Dauki fault during the dextral strike slip movement. Thus the net slip for Dauki fault involves a vertical component and a dextral strike slip component (oblique-slip fault).[9]
References
- ^ Md Shofiqul Islam, The Dauki fault at the Shillong plateau-bengal basin boundary in northeastern India: 2D finite element modeling, Journal of Earth Science
- ^
- ^ a b Fault, Banglapedia, Asiatic Society Bangladesh
- ^ P. Evans (1964) The Tectonic framework of Assam, Geological Society of India, vol. 5 pp.80–96
- ^ Murthy et al (1969), ‘’The Dauki Fault of Assam’’, Oil and Natural Gas Commission Bulletin, vol 6 (2), pp 57–64
- ^
- ^ Yeats et al (1997), The geology of earthquakes, Oxford University Press, p. 568
- ^ J.D. Das et al, Fault tectonics of the Shillong plateau and adjoining regions, north-east India using remote sensing data, International Journal of Remote Sensing
- ^ V. Srinivasan (2005), The Dauki fault in Northeast India: Through remote sensing. Journal of the Geological Society of India. 66. 413–426.