Bangladesh at high quake risk for its geographic location
Although Bangladesh bears no relation with the recent devastating earthquake and tsunami in Japan, the country is highly vulnerable to tremors due to its geological structure, tectonic set-up and geographical location.
According to a geologist, Bangladesh is located in the northeastern part of the Indian sub-continent at the head of the Bay of Bengal. Tectonically, it lies on the northeastern Indian plate near the edge of the Indian carton and at the junction of three tectonic plates - the Indian Plate, the Eurasian Plate and the Burmese microplate.
Dr Syed Humayun Akhter, Professor of Geology, Dhaka University, said these form two long active tectonic structures where plates converge - the India-Eurasia plate boundary to the north forming the Himalaya Arc, and the India-Burma plate boundary to the east forming the Burma Arc.
“Bangladesh and Japan are situated in two distinct geological and tectonic locations separated by the 5000km wide Eurasian plate. There is no link between the Japanese earthquake and the seismicity in Bangladesh.”
He informed that Japan is located in the Circum Pacific Seismic belt, also known as the Pacific Ring of Fire, where 90 percent of the world's tremors occur. Only seven percent occurs in Alpide-Himalayas-Java-Sumatra seismic belt, and two percent in the Mid-Atlantic Ridge seismic belt. Bangladesh belongs to the Alpide-Himalayas seismic belt with low earthquake frequency.
The geologist, however, said the Indian plate is moving 6cm each year towards the northeast, and sub-ducting under the Eurasian plate at 45mm and the Burmese plate at 35mm in the north and east respectively each year. This continuous motion is taken up by active faults.
He said the probability of an earthquake from a given fault depends on the rate of motion and on the time since the last rupture. Active faults of regional scale capable of generating moderate to great earthquakes are present in and around Bangladesh.
Prof Humayun said these include the Dauki fault, about 300km long trending east-west and located along the southern edge of the Shillong Plateau (Meghalaya- Bangladesh border), the 150km long Madhupur fault trending north-south situated between Madhupur Tract and Jamuna flood plain, the Assam-Sylhet fault, about 300km long trending northeast to southwest located in the southern Surma basin, and the Chittagong-Myanmar plate boundary fault, about 800km long running parallel to the Chittagong-Myanmar coast.