700 years of built-up stress could trigger two Mw 8.8 earthquakes in Himalayas, study warns

The entire Himalayan region was recently classified into the newly introduced highest-risk Zone VI in the newly released and revised seismic hazard map. More than 60 per cent of the country is under moderate to high earthquake risk zones. Earlier, in October, a study flagged the risk of massive earthquakes in the Himalayas, stating that the region could witness two high-intensity quakes in the future. KM Sreejith and his team measured both horizontal and vertical surface displacements to understand megathrust transitions, and "moment deficit and the spatial distribution of fault locking." Studying a stretch of approximately 800 km along the Himalayas revealed that the region is at risk of increased seismic hazard and could witness two 8.8 moment magnitude (Mw) earthquakes. Rishav Mallick, Eric J Fielding, MCM Jasir, Mark Simons and Ritesh Agrawal were also part of the research team.

The researchers noted in the study titled "Geodetic Insights to the Himalayan Megathrust Kinematics Unravel Increased Earthquake Hazard" that the earthquakes will release "interseismic strain" accumulated over 500-700 years. "The present analysis with improved geodetic observations and models suggests higher convergence and wider locking width for the Himalayan megathrust, implying an increased seismic hazard," the authors wrote.

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"Earlier Himalayan studies relied only on horizontal velocities from Global Navigational Satellite Systems, leaving details of how the megathrust transitions from locked to steady interseismic creep poorly constrained," they stated. But the latest method allowed for "measurements of both horizontal and vertical surface displacements."

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Land under Himalayas is slowly rising upwards

The researchers measured how the Earth’s surface in the Himalayas is moving right now using precise radar and satellite-based tools. They found that, over large parts of the "higher Himalayas," the land is slowly rising vertically, at a rate of about 5 to 8 millimetres per year, or about 0.5 to 0.8 metres every century. While this might not sound like much, it is a continuous process, proving that the Himalayas are still active. Tectonic forces are pushing and deforming the crust in real time today. This slow rise and deformation have led to stress being accumulated along the big fault zone under the mountains, which is the Main Himalayan Thrust. Scientifically speaking, this activity could lead to a massive earthquake.