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Brief description of earthquakes considered in this study are presented below:
1885 M=7.0 Great Bengal Earthquake: This earthquake with a magnitude of 7.0 occurred on 14th August, 1885 with epicenter at 24.70°N, 89.55°E. The main shock was strong enough to destroy numerous houses and important public buildings. Poor quality constructions were one of the main causes of damage. The main shock was followed by a series of aftershocks and the earthquake was associated with significant ground rupture. The shaking was strongly felt in Sirajganj, Bogra, Rangpur, Sherpur, Mymensingh, Jamalpur, Dhaka, and Pabna where destruction to building was the greatest and loss of life had occurred. It extended westwards into Chota Nagpur and Bihar, Northwards into Sikhim and Bhutan and eastwards into Assam, Monipur and Burma. From the analysis of the macroseismic data, the isoseismal intensity at around 80 km distance was estimated as VII.
1897 M=8.1 Great Indian Earthquake: The powerful Great Indian Earthquake of 12th June 1897 occurred with epicenter at 25.84°N, 90.38°E in Assam. The focal depth was reported to be 60 km. Although the initial magnitude was reported to be 8.7, it was later reported as 8.0-8.1 by Ambraseys and Bilham (2003). The earthquake almost totally destroyed settlements and small towns on the western part of the Shillong Plateau, and caused heavy damage in surrounding districts, chiefly due to the extensive liquefaction of the ground. Ambraseys and Bilham (2003) re-estimated the intensity levels, intensity in Dhaka for this earthquake was VI. They maintained that Oldham's intensities (Oldham, 1899) were unsuspectingly inflated by 1.5-3 intensity units. The large area over which loose deposits liquefied and the size of the area over which the shock was felt, are similar to those produced by other large earthquakes of New Madrid 1811, Bihar-Nepal 1934 and Assam 1950. The epicentral area is in the west-central part of the Shillong Plateau, with intensities decaying to the north and south at the same rate.
1918 M=7.6 Srimangal Earthquake, 1918: The Srimangal earthquake of July 8, 1918 occurred at 24.25°N, 91.80°E. Reported focal depth was around 14 km. Magnitude was reported to be 7.6. The main shock which lasted about 12 secs damaged almost every house in the epicentral area. The greatest damage occurred in the tea garden areas of the Balisera, Doloi and Luskerpore valleys. With few expectations all brick buildings were found to be destroyed within this area. Water and sand spouted up to a height of several feet. Most of the area where the earthquake was violent enough damaged all or nearly all brick buildings.
1930 M=7.1 Dhubri Earthquake: The Great Dhubri Earthquake of July 1930 occurred at. 25.95°N, 90.04°E. Reported focal depth was around 60 km. Magnitude was reported to be 7.1. Aftershocks occured at regular intervals throughout the July 1930. The earthquake caused total destruction or heavy damage to most of the constructions in the area around the villages of Dhubri. Ground fissure and liquefaction-induced damages were majority in the zone covering the towns of Rangpur, Lalmanirhat, Cooch Bihar, Alipur Duar, eastern region of Brahmaputra River, and Tura town in Garo hills. This earthquake had disastrous result in northern Bengal and in Western Assam and was felt very distinctly over a wide area, extending from Dibrugarh and Manipur in the east to Chittagong and Calcutta in the South to Patna in the west and beyond the frontiers of Nepal, Sikkim and Bhutan in the North.
1945 M=6.7 Mikirhills Earthquake: The Earthquake was felt during 8th July, 1945. Magnitude was reported to be 6.7. The Epicenter was 25.8°N, 92.3°E. The epicentral distance of the third isoseist (IV-MMI) was considered as 260 km.
1964 M=5.5 Medinipur Earthquake: The Earthquake occurred on 15th April, 1964 with a reported magnitude of 5.5. Focal depth was reported to be around 36 km. The Epicenter was 21.7°N, 88°E in the coastal area. The mean epicentral distance of the third isoseist (III-MMI) was considered as 162 km.
1999 M=5.1 Moheshkhali Earthquake, 1999: The Earthquake of magnitude 5.1 and focal depth 10 km occurred on 22th July, 1999. The Epicenter was 21.61°N, 91.96°E near Moheshkhali island. The mean epicentral distance of the third isoseist (V-MMI) was considered as 17.5 km.
Posted in: Regional Earthquakes
