Complex Tectonics In Northeastern Fringe Linked With ‘Great Assam Earthquake 1950’ : Study 

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Researchers have linked the complex tectonics of the North Eastern fringe of the Indian Plate in the Eastern Himalaya and the Indo-Burma Ranges (IBR) with the ‘Great Assam Earthquake 1950’.

According to PIB report, interactions between the two tectonics can result into deeper earthquakes along the IBR and crustal earthquakes in the Eastern Himalaya.

The Indian Plate’s north-eastern border in the Eastern Himalaya has been found to be seismically active till a depth of around 40 kms, whereas the Indo-Burma Ranges (IBR) has been found to be seismically active upto a depth of roughly 200 kms.

“This seismic structure is part of a complex tectonic system that caused the huge Assam earthquake of 1950 (Magnitude 8.6) and is now accumulating stress in preparation for a future earthquake. The Great Assam Earthquake, which struck in the Mishmi Hills in the Arunachal Himalaya, was the greatest intra-continental earthquake ever recorded.” – stated the report.

The Eastern Himalayan Syntaxis (EHS) in Arunachal Pradesh and neighbouring Assam is regarded as one of the world’s most seismically active areas.

Besides, the northeastern corner of the Indian Plate in the EHS is classified as seismic zone V on India’s national zoning map, and it has the potential to cause severe earthquakes in the future.

Since the great Assam earthquake of 1950, there have been no large earthquakes along the region between upper Assam and the Mishmi Block, hence its considered a seismic gap region.

A locked zone was discovered in the Mishmi Thrust (MT) zone during earlier studies, which could indicate tension buildup ahead of an earthquake.

A study led by Dr. Devajit Hazarika of the Wadia Institute of Himalayan Geology used micro and moderate magnitude earthquakes recorded at local seismological stations to highlight the overall seismicity pattern in the EHS and adjoined Indo-Burma Ranges (IBR), with a focus on the seismotectonic of the Lohit Valley region.

Its worthy to note that the ‘Great Assam Earthquake 1950’ – leaving trails of devastation in Assam and Tibet, had a calculated magnitude of 8.6.

The natural catastrophe has been proclaimed as one of the critical disasters, since the introduction of seismological observing stations.

Many rock falls in the Mishmi Hills, as well as the removal of forest regions, altered the relief. The tributaries of the Brahmaputra were blocked; one in the Dibang valley burst without inflicting harm, but the one at Subansiri opened after an 8-day delay, submerging numerous hamlets and killing atleast 532 people.

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