Study reveals earthquake sources of India's eastern most part
The Himalaya takes a sharp southward bend and connects with the Indo-Burma Range in the Tuting-Tidding Suture Zone (TTSZ) of the Eastern Himalayas. This part of the Arunachal Himalaya has gained significant importance in recent times due to the growing need of constructing roads and the hydropower projects.
A new study about earthquakes in the Arunachal Himalayan region has found that the area is generating moderate earthquakes at two different depths: Low magnitude earthquakes are concentrated at 1-15 km depth and slightly higher than 4.0 magnitude earthquakes are mostly generated from 25-35 km depth.
The study by the Wadia Institute of Himalayan Geology, which looked into the elastic properties of rocks and seismicity in the eastern most part of the country, found that the intermediate-depth is devoid of seismic activities.
A seismicity study conducted by Wadia Institute of #Himalayan Geology under the Department of Science & Technology, has revealed that Arunachal Himalayas are generating low to moderate earthquakes at two different crustal depths.@IndiaDST @PMOIndia @moesgoi pic.twitter.com/rqPQIfwiFb— Dr Harsh Vardhan (@drharshvardhan) July 25, 2020
The exhumation and growth of the Himalaya is a continuous process as the Indian plate slides under the Eurasian plate. This process keeps modifying the drainage patterns and landforms and is the pivotal reason for causing an immense seismic hazard in the Himalayan mountain belt and adjoining regions, necessitating assessment and characterization of earthquakes in terms of cause, depth and intensity before construction activities are initiated.
According to the study, the crustal thickness in the Arunachal Himalayan reegion varies from 46.7 km beneath the Brahmaputra Valley to about 55 km in the higher elevations, with a marginal uplift of the contact that defines the boundary between crust and the mantle technically called the Moho discontinuity. This, in turn, reveals how the Indian plate slides below the Eurasian plate in the Tuting-Tidding Suture Zone.
"[In the] Tuting-Tidding Suture Zone (TTSZ) of the Eastern Himalaya, the Himalaya takes a sharp southward bend and connects with the Indo-Burma Range. This part of the Arunachal Himalaya has gained significant importance in recent times due to the growing need of constructing roads and the hydropower projects, making the need for understanding the pattern of seismicity in this region critical," said an official statement about the study.
This detailed assessment of seismicity in this region will be helpful for planning any large scale construction in this region in the future, it added.
The study, published in the 'Journal of Asian Earth Sciences', also indicated the presence of fluid or partial melt at crustal depths at higher parts of the Lohit Valley.
The team of scientists led by Dr. Devajit Hazarika installed 11 broadband seismic stations along the Lohit River Valley of Arunachal Himalaya to understand the elastic properties of rocks and seismicity in this easternmost part of India.In the present study, the WIHG team used both teleseismic (earthquakes that occur more than 1000 km from the measurement site) and local earthquake data with the help of seismometers having a flat velocity response for the frequency range of 0.004-35 Hz.
Data were continuously recorded at 20 samples per second, and the Global Positioning System (GPS) receivers were used for time synchronisation.
The study which used tele-seismic and local earthquake data procured during January 2007-June 2008 has helped map under-thrusting in this easternmost part of the country and can not only help plan construction but also improve earthquake preparedness in the area.
(With inputs from PTI)