Uttarakhand sits on locked 115 km fault line storing strain for a magnitude 8.1 earthquake

The 115-kilometer segment of the Main Himalayan Thrust (MHT) fault located underneath Uttarakhand is completely coupled and accumulating huge amounts of tectonic stress underground, according to a joint study conducted by researchers from IIT Bombay and several other foreign geoscientists.

The study, which was published under the name "Evidence of Strong Plate Coupling in the Uttarakhand Himalayas: Constraints from GNSS and ALOS-2 InSAR Observations," concludes that tectonic strain builds up at a speed corresponding to an 8.1 magnitude earthquake occurring once in a hundred years.

How the locked fault builds up tectonic energy

The Indian tectonic plate moves towards the Eurasian plate at the speed of 18 millimeters per year. But since the fault interface underneath Garhwal and Kumaon is locked, smooth movement is impossible.

Upheaval metrics: The blocked horizontal sliding causes the upper Himalayas to move upward at the speed of 4 to 6 millimeters per year.

Elastic strain buildup: Locked fault acts like a stretched rubber band, accumulating elastic strain within the Central Himalayan Seismic Gap—an area where there has been no fault clearing earthquake for hundreds of years.

Data fusion: Scientists including Dibyashakti Panda, Mridul Yadav, Eric O. Lindsey and G. Srinivasa Rao utilized satellite positioning (GNSS) technology in conjunction with Japan’s ALOS-2 satellite radar interferometry to delineate the fault coupling.

A magnitude rupture will have a wider impact than just the hills

It is important to remember that a high-magnitude rupture of the MHT will affect areas far beyond just the hills. The seismic shocks would have serious implications for urban centers located in the plains.

"There can be no exact prediction about when the earthquake will happen, but the probability of a magnitude 7.5 to 8.0 event is very likely. This is something that is only a matter of time," said Dr. Naresh Kumar, geologist at the Wadia Institute of Himalayan Geology.

These densely populated cities such as Delhi, Lucknow, Kanpur, and Patna are constructed on an alluvial soil in the Indo-Gangetic plains. This increases their vulnerability to long-period seismic waves that are emitted from major faults ruptures.

Imperative of building code compliance and disaster preparedness

The paper stresses the importance of structural mitigation measures as an urgent need. The fast-paced urbanization of the Himalayas region without due compliance with the seismic building code makes the region vulnerable.

Key administrative and structural considerations would include:

Mandatory audits: Structural strengthening of existing public facilities such as buildings, schools, and hospitals in high-risk seismic areas.

Geological mapping: Mandatory geological audit prior to any heavy infrastructure and tourism construction in deep gorges.

Sensor networks: Establishment of ground-based GNSS network in Central Seismic Gap to detect the subtle crustal deformations.