GUWAHATI: Scientists have found the first geological evidence of an earthquake at Himebasti village along the Assam-Arunachal Pradesh border recorded by historians as Sadiya earthquake, which is recorded to have caused massive damage in the area and the region in 1697 CE.
This finding could lead to a seismic hazard map of the eastern Himalayas, which could promote the region’s construction and planning.
Historical records refer to often recurring earthquakes in the eastern Himalayas for which there is no geological evidence, raising the question of whether these events have breached the surface or remained blind and how they contribute to the region’s seismic budget, home to millions of people.
A mega trench excavation at Himebasti village in the region was carried out by scientists from Wadia Institute of Himalayan Geology (WIHG), a research institute under the department of science and technology (DST) of the government of India, where the most recent occurrence which imprints and analyses the 1697 Sadiya earthquake with modern geological techniques.
The scientists have found the first geological surface rupture signatures in the form of exposed deposits connected with rivers and streams deformed by a thrust fault along a northeast dipping fault zone.
The team dated 21 radiocarbon samples from the trench exposure to constrain the causative faulting event at the site.
They also found large tree trunks stuck in the youngest flood deposits at the exit of the Subansiri river indicating the post-seismic aggradation of the river following a number of earthquakes till six months in an abortive fashion.
Study of the Sadiya earthquake on the grassy plain nearly surrounded by the forested eastern Himalayas on the right bank of the Lohit river adds a significant site to the eastern Himalaya seismic hazard assessment, that will benefit the residents and help in providing better infrastructure across the eastern Himalayan foothills which is one of the most densely populated regions in the world.
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