Contrary to the conventional belief, the faultline in Ladakh region, where the India and Asian Plates are joined, has been found to be tectonically active, suggesting that the rocks along the fault zones are very weak and fragile.
So, in terms of landslides due to rainfall, it has much more implications, said Indian scientists in a study published in the journal ‘Technophysics’. Earlier, the suture zone was conventionally thought to be locked.
India and Asian Plates are joined at the suture zone of the Himalayas or the Indus Suture Zone (ISZ) in the Ladakh region.
The findings could have major implications in terms of earthquake study, prediction, understanding the seismic structure of the mountain chains well as its evolution. The Scientists from Wadia Institute of Himalayan Geology (WIHG), Dehradun, an autonomous institute under the Department of Science and Technology, found through observations and detail mapping of geological features that the suture zone of Himalaya that was conventionally thought to be locked is tectonically active.
The Indus-Tsangpo suture zone marks the limit of the Indian plate where it collided with the Asian plate.
“Since we have shown that fault in this area (Ladakh) is also active, the rocks along the fault zones are very weak and fragile. So, in terms of landslides it has much more implications. Seismically, this area is also active, but the activity is very low to moderate.
“If there is any major rainfall event along the Indus river fault, it is more prone to landslides,” said Koushik Sen, one of the co-authors of the paper.
The geologists observed that sedimentary beds are tilted and thrust broken, the rivers are associated with uplifted terraces, and the bedrock shows brittle deformation that occurred at much shallower depths.
These deformed geological features were then dated in the laboratory at Dehradun using a technique called Optically Stimulated Luminescence (OSL) (method for carrying luminescence dating of geological sediments)and data of seismicity and denudation rate was reviewed.
The combination of field and lab data suggested the region of the Indus Suture Zone (ISZ) has been neo-tectonically active since the last 78,000-58,000 years and a recent earthquake in 2010 of low magnitude 4.0 near the village of Upshi occurred due to a thrust rupture.
Himalaya were known to be made up of north dipping thrusts like the Main Central Thrust (MCT), the Main Boundary Thrust (MBT), and the Main Frontal Thrust (MFT).
As per the established models, all of these thrusts except MFT are locked, and overall deformation in the Himalayas is being accommodated only along with the MFT.