Study attributes tectonic linkage in the northeast edge of the Indian plate to great Assam Earthquake

New Delhi: Researchers have traced the great Assam Earthquake to complex tectonics of the North Eastern fringe of the Indian Plate in the Eastern Himalaya and the Indo-Burma Ranges (IBR) and the interactions between the two, which can produce deeper earthquakes in IBR and crustal ones in the Eastern Himalaya.

The north-eastern fringe of the Indian Plate in the Eastern Himalaya has been found to be seismically active up to about 40 km depth, while the seismicity in the Indo-Burma Ranges (IBR) is observed up to a depth of around 200 km.

They have suggested that this seismic structure forms a complex tectonics which produced the great Assam earthquake of 1950 (M 8.6) and maybe building up stress for a future earthquake. –The Great Assam Earthquake is the largest intra-continental earthquake ever recorded, which was located at the India-China border near the Mishmi Hills of Arunachal Himalaya.

The Eastern Himalayan Syntaxis (EHS) in Arunachal Pradesh and bordering regions of Assam is acknowledged as one of the most seismically active regions in the world. The northeast corner of the Indian Plate in the EHS belongs to the seismic zone V of the national zoning map of India and does have a potential to trigger major earthquakes in the future.

In contrast to several studies carried out in the EHS and adjoining SE Tibetan plateau, extremely less studies have been done in the north-eastern fringe of the Indian Plate in the Eastern Himalayan Syntaxis (Tidding-Tuting Suture, TTSZ) for understanding seismogenesis and its tectonic linkage. After the 1950 great Assam earthquake, the region between the upper Assam and the Mishmi Block is not producing any large earthquakes and is considered as a seismic gap region. A previous study has suggested a locked zone in the Mishmi Thrust (MT) zone, which may suggest building up of stress for a future earthquake.

Moderate magnitude earthquakes in the region are rarely reported by global seismological networks. To obtain information of moderate and microearthquakes, the Wadia Institute of Himalayan Geology, Dehradun, an autonomous institute of the Department of Science and Technology, established 11 broadband seismological stations in the Lohit Valley and 8 stations in the Siang Window of Arunachal Himalaya.

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