New Delhi, June 1 (SocialNews.XYZ) Indian plate subduction stops north of 27N latitude and indentation process is responsible for seismicity in region linked to 1950 Assam earthquake (magnitude 8.6), study finds .
The study also suggested that the Indo-Burma Range (IBR) is more susceptible to deeper earthquakes, while crustal scale earthquakes are more likely to occur in the eastern Himalayan syntax ( EHS).
The Eastern Himalayan Syntax (EHS) on the eastern foothills of Arunachal Pradesh and adjoining regions of Assam is recognized as one of the most seismically active regions in the world.
The northeast corner of the Indian plate in the EHS belongs to seismic zone V of the national zoning map of India and has the potential to trigger major earthquakes in the future.
The researchers analyzed seismic data recorded by the local broadband seismograph network as well as data from the International Seismological Center catalog for seismicity in the northeast fringe of the Indian Plate in the EHS (Tidding-Tuting Suture) and adjacent areas.
The study published in Tectonophysics Journal also found that the Tidding-Tuting Suture Zone is seismically active down to about 40 km depth. Another major finding is that the Mishmi, Tidding and Lohit thrusts are steeply dipping thrust faults while the Walong fault is a strike-slip fault with a minor thrust component. (All places in Lohit district of Arunachal Pradesh).
“The TTSZ is seismically active down to about 40 km depth. In contrast, seismicity in the Indo-Burma Ranges (IBR) is observed down to a depth of about 200 km, suggesting active subduction (a term borrowed from oceanography, which refers to the converging-margin tectonic process by which slabs of oceanic lithosphere descend into the mantle) Indian plate process below the IBR This suggests that the IBR is more sensitive to deeper earthquakes, while crustal scale earthquakes are more likely to occur in the TTSZ,” the study states.
This research suggests that the subduction process terminates north of about 270 N latitude and that the indentation process of the rigid Indian plate in Southeast Asia primarily controls seismicity north of the IBR.
“This seismic structure forms a complex tectonics, which produced the Great Assam earthquake in 1950 and could create tension for a future earthquake. The Great Assam earthquake is the largest earthquake in intracontinental land ever recorded,” he said.
Unlike several studies conducted in the EHS and the adjoining SE Tibetan Plateau, the northeast fringe of the Indian Plate in the EHS (TTSZ) is extremely understudied to understand seismogenesis and its tectonic linkage.
A team led by Dr Devajit Hazarika from the Wadia Institute of Himalayan Geology, Dehradun, an autonomous institute of the Department of Science and Technology, has established 11 broadband seismic stations in the Lohit valley and eight stations in the Siang window of ‘Arunachal Himalayas for information on moderate and micro earthquakes in the region.
The results reveal that the closely spaced Mishmi, Tidding and Lohit faults along the Lohit and Dibang river valleys in eastern Arunachal Pradesh are steeply dipping thrust sheets that accommodate great crustal shortening. due to the indentation process and clockwise rotational tectonics.
The Walong Fault in the upper Lohit River Valley in Arunachal Pradesh is characterized by strike-slip movement with a thrust component that facilitates clockwise rotation of crustal material around the syntax.