Out-of-sequence thrusting (OOST) in the Himalaya: insights from the Geil-Khola thrust fault zone in the Ramgarh thrust sheet, Darjeeling Himalaya, India
Dr Vinee Srivastava’s research group at the Department of Earth and Environmental Sciences conducted a detailed study on an out-of-sequence thrust (OOST) fault in the Himalaya, specifically the Geil-Khola Thrust fault in the Darjeeling region. Out-of-sequence faults significantly impact society as they are linked to major earthquakes, such as the devastating 2015 Nepal Earthquake, and are associated with increased landslide activity. The study highlighted the internal architecture of the Geil-Khola OOST, revealing a complex interaction between climate-induced exhumation and tectonic deformation over geological timescales. The applications of solid mechanics and materials science principles indicate that deformation initially occurred at depths of 12-14 km via dislocation creep at around 350°C. Climate forces subsequently brought these rocks closer to the surface, where they were reactivated by frictional sliding, causing topographic changes and posing seismic hazards akin to the 2015 events. This frictional sliding altered the rocks' rheological properties, leading to slope failures and multiple landslides. The findings underscore the need for a multidisciplinary approach to better understand Himalayan faults, essential for disaster risk reduction, community protection, and safe infrastructure development in this vulnerable region, particularly where roads and hydropower assets are concentrated.For more details, kindly visit https://doi.org/10.1016/j.jsg.2026.105774
