The Himalayas, the world's youngest and most dramatic mountain range, harbor secrets deep beneath their towering peaks that could profoundly impact earthquake risks for over a billion people in South Asia. Recent geological research has uncovered a 'hidden seismic process' where the Indian tectonic plate is not simply sliding uniformly under the Eurasian plate but is instead warping, tearing, and delaminating at depths around 100 kilometers. This revelation, drawn from advanced seismic imaging techniques, challenges long-held assumptions about Himalayan tectonics and elevates concerns for future seismic events in India, Nepal, Bhutan, and beyond.
Formed by the ongoing collision between the Indian and Eurasian plates over 50 million years ago, the Himalayas experience immense compressive forces. Traditionally, models depicted the Indian plate underthrusting smoothly beneath Tibet. However, new studies using three-dimensional seismic tomography and S-wave receiver functions reveal a more complex picture: in the eastern Himalayas, particularly around 90° to 92° east longitude near rift zones like Yadong-Gulu and Cona-Sangri, the denser lithospheric mantle is peeling away from the lighter crustal layer, sinking into the mantle and creating an asthenospheric wedge of molten rock. This delamination process redistributes stress, potentially loading adjacent faults and increasing the likelihood of moderate to major earthquakes.
🧭 Decoding the Delamination: How Seismic Imaging Revealed the Hidden Rift
Geophysicists Simon Klemperer from Stanford University and Fabio Capitanio from Monash University presented groundbreaking findings at the American Geophysical Union (AGU) meeting in late 2025, utilizing S-wave receiver function analysis—a method that examines how seismic waves refract at layer boundaries deep underground. Their work shows the Indian plate's lower layer detaching, evidenced by helium isotope anomalies in Tibetan hot springs and clusters of deep mantle earthquakes. While primarily international, this aligns with complementary Indian efforts at institutions like the Wadia Institute of Himalayan Geology (WIHG) in Dehradun, which has long pioneered subsurface imaging in the region.
WIHG's broadband seismic networks have mapped fault structures and attenuation characteristics across northwest and northeast Himalayas, contributing to probabilistic seismic hazard assessments. Their studies highlight how such delamination could propagate southward, influencing the Main Himalayan Thrust (MHT)—the primary fault responsible for great earthquakes. Step-by-step, the process unfolds: (1) Compressive forces buckle the plate; (2) Density contrasts cause the mantle lithosphere to founder; (3) This peeling induces crustal extension, forming rifts; (4) Released fluids lubricate faults, potentially triggering slip.
In parallel, a February 2026 study in Science by Shiqi Wang and Simon Klemperer mapped rare continental mantle earthquakes globally, finding dense clusters beneath the Himalayas. These 'deep' events (below the Moho discontinuity) are 100 times rarer than crustal quakes but signal mantle convection recycling subducted material, linking surface risks to profound geological dynamics.
Central Himalayan Seismic Gap: Strain for Twin Megaquakes
Compounding the delamination concerns is research on the central Himalayan seismic gap—a 500-km stretch from Kathmandu to Garhwal silent for major quakes since 1505 CE. Led by K.M. Sreejith from the Space Applications Centre (ISRO), Ahmedabad, a 2025 Geophysical Research Letters paper integrates ALOS-2 InSAR satellite data and GNSS observations to quantify interseismic strain. Findings: vertical uplift of 5-8 mm/year indicates a 115-km-wide locked zone on the MHT accumulating stress at 20-22 mm/year convergence.
This ISRO-led study estimates enough stored energy for two Mw 8.8 events—or potentially one Mw 9 rupture—posing catastrophic threats to densely populated Indo-Gangetic plains. Paleoseismic trenches confirm prior great quakes in 1344 and 1505 CE, underscoring the gap's overdue status. Indian researchers emphasize that soft sediments in cities like Delhi amplify shaking, with long-duration ground motions exacerbating damage.
India's Updated Seismic Zonation Map: Himalayas in Zone VI
In response, India's Bureau of Indian Standards (BIS) released IS 1893 (Part 1):2025 in November 2025, reclassifying the entire Himalayan arc into Zone VI—the highest risk category. Spearheaded by WIHG under Director Vineet Gahalaut (former National Centre for Seismology head), the map employs probabilistic seismic hazard analysis (PSHA), factoring active faults, max magnitudes, and site effects. Previously split across Zones IV-V, the unified high-risk status reflects locked segments and southward rupture potential.
WIHG's contributions include high-resolution fault mapping and attenuation models for northwest Himalaya, revealing underestimated stresses. Over 61% of India now in moderate-high zones, urging retrofits for critical infrastructure. New codes mandate pulse-like ground motion consideration near faults, liquefaction mitigation, and performance-based design ensuring hospitals/schools remain operational post-quake.
Contributions from Indian Higher Education Institutions
Indian universities and research bodies are at the forefront. IIT Bombay's studies on Indo-Gangetic heatwaves link to seismic-thermal interactions, while IISc Bengaluru models tectonic stresses. IIT Guwahati's fuzzy optimization for green transport indirectly aids hazard-resilient planning. WIHG, affiliated with IIT Roorkee collaborations, deploys seismic arrays imaging MHT geometry.
ISRO's SAC integrates SAR/InSAR for strain mapping, training geophysicists via M.Tech/PhD programs. Universities like IIT Kharagpur and Delhi University host paleoseismology labs trenching ancient ruptures. These efforts, funded by MoES/DST, produce actionable data for NDMA, fostering interdisciplinary PhD research in tectonics and hazard modeling.
Risks Amplified: Population Centers in the Crosshairs
With 240 million in Himalayan foothills and 400 million in Indo-Gangetic plains, a Mw 8.8 quake could kill tens of thousands, as modeled by WIHG. Delhi (Zone IV but near Zone VI) faces 1-2g peak ground acceleration; Kathmandu's basin amplifies waves 3-5x. Landslides, common in monsoons, compound risks—2023 Sikkim flash flood killed 50+.
Statistics: Himalayas host 20% global continental quakes; 1905 Kangra (Mw7.8) killed 20,000; 2015 Gorkha (Mw7.8) 9,000 dead. Delamination adds unpredictability, with mantle quakes foreshadowing crustal slips. Bhutan/Nepal share vulnerabilities, demanding transboundary early warning.
From Research to Resilience: Mitigation Strategies
- Advanced Monitoring: Expand GNSS/InSAR networks (NISAR mission 2026); AI-driven earthquake forecasting via IIT Madras SWAYAM courses.
- Building Codes: Enforce BIS 2025—ductile designs, base isolation for high-rises.
- Land Use Planning: Relocate from floodplains; landslide zoning via WIHG models.
- Education & Drills: University-led awareness, NEAMTWS integration.
- International Collaboration: RANET for South Asia alerts.
Govt initiatives: ₹10,000 crore National Earthquake Risk Mitigation Project; IIT-Delhi's retrofitting tech for schools.
Future Outlook: NISAR and Beyond
Upcoming NASA-ISRO NISAR (2026 launch) promises cm-level strain mapping, revolutionizing forecasts. Ongoing WIHG seismic arrays target blind thrusts; IISER Bhopal refines methane emission models tying to tectonics. Challenges persist: funding gaps, urban sprawl. Yet, Indian research positions South Asia as a leader in collision-zone seismology, turning hidden dangers into predictive power.
Photo by Harish Bharti on Unsplash
Stakeholder views: NDMA Director warns of 'quake bomb'; WIHG's Gahalaut stresses PSHA urgency. Bhutanese geologists collaborate on cross-border faults. Outlook: With proactive research from Indian academia, South Asia can mitigate the Himalayan threat, safeguarding lives amid tectonic fury.