Scientists in India found that Himalayas are not uniform and assume different physical and mechanical properties (a property present in crystals called anisotropy) in different directions that could trigger large tremors. Researchers from Wadia Institute of Himalayan Geology (WIHG), Dehradun, and IIT, Kharagpur found that the North-West Himalayan region exhibited a peculiar characteristic present in crystals.
Himalayan region witnessed four major tremors in 20th century
The study gains significance when looking at the history of the quakes in the Himalayan region from Garhwal and Himachal Pradesh, which witnessed four destructive moderate to great earthquakes since the beginning of the 20th century. The region witnessed the Kangra earthquake of 1905, the Kinnaur earthquake of 1975, the Uttarkashi earthquake of 1991 and the Chamoli earthquake of 1999.
The joint study used seismic waves from 167 earthquakes recorded by 20 broadband seismic stations deployed in the Western Himalaya. They said that the major contribution of the anisotropy is mainly because the strain induced by the Indo-Eurasia collision (going on since 50 million years) and deformation due to the collision is found to be larger in the crust than in the upper mantle.
VARIATION OF HIMALAYAN THRUST
The inhomogeneity along the Himalayas influences the stressing rate because of variation in the geometry of the Main Himalayan Thrust (MHT) system, and it controls the rupture size during the earthquake. This lack of homogenous physical and mechanical properties of the Himalayas could help explore new perspectives about deformations taking place at the Himalaya-Tibet crustal belt involved in the formation of the Himalayan Mountains.
Wadia Institute of Himalayan Geology is an autonomous institute under the Department of Science and Technology. Dr. Sushil Kumar, Scientist ‘G’, WIHG; Shubhasmita Biswal, Researcher, WIHG, Mahesh Prasad Parija, Ex-Researcher, WIHG and IIT KGP William Mohanty were involved in the study.