GUWAHATI, April 19 - There may not be any likelihood of a major earthquake shaking the NE region of the country in the next around 150 years, if the present geo-tectonic condition of the Indo-Australian (Indian in brief) Plate persists. This is the observation made by Dilip Kumar Barman, a former senior geologist of the State�s Directorate of Geology and Mining. Barman is known for his thorough study of the geo-tectonic setting of the NE region.
Barman, who was talking to this correspondent, justified his point by saying that the re-activation of the volcano on the Barren Island located on the Bay of Bengal, on March 29, 1991, after a gap of around 150 years, has reduced the seismic stress on the Indo-Australian Plate, � particularly in the NE region of India.
The seismic stress that prevailed in this part of the globe during the 1897 and 1950 earthquakes has now been reduced by the movement of the magma from the Indian Plate due to the convection current. The Indo-Australian Plate is pushing itself below the Eurasian Plate in its north-east-ward move. Because of this subduction or convergence of the Indian Plate, the tip of this plate is melting under the impact of the natural radio activity and the magma (viscous rock) is thus produced.
This magma forms a seething condition and due to the convection current, the magma moves towards the South East Asian Volcanic belt located on the meeting points of the Indo-Australian Plate, Eurasian Plate and the Pacific Plate. A large number of active volcanoes are located in this belt and they are throwing up lava and forming mountains, Barman said.
In India, the volcano on the Barren Island, at a distance of around 150 km from Port Blair, is an active one and its activation in 1991 resulted in reduced stress on the Indo-Australian Plate, � particularly in the North Eastern part of India, he said.
Therefore, there may not be any possibility of a major earthquake occurring in the NE region of India and its neighbouring Indo-Australian Plate areas in the near future, at least for the next 150 years, Barman maintained.
He explained that major earthquakes occur mainly due to two geological conditions. One of them is Intra-Plate seismic activities. Such activities resulted in the 1897 earthquake, which finally led to the creation of many faults within the plate and heavy landmass subsidence, leading to the creation of the Chandubi Beel in Kamrup district and elimination of the Saulkhowa River in the present-day Barpeta district.
The other condition is the Inter-Plate tectonic movement, which causes earthquakes on the boundaries of two plates, like the Indo-Myanmar border region, where there exists a Benioff Zone �meaning existence of innumerable earthquake epicentres.
He said earthquakes of lesser intensity like the ones that rocked the NE region in January and April this year, may continue to occur intermittently under the impact of the compressional force resulting from the post-collision adjustment (after the creation of the Himalayas resulting from the compressional force generated by the collision of the Indian Plate with the floor of the shallow sea Tathis) and the subduction of the Indian Plate along the Indo-Myanmar border region.
However, he clarified that even the impacts of moderate earthquakes become massive when the depth of their occurrence (that is focus) is shallow.