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Fault Geometry Control on Earthquake Segmentation and Locking Transition on Mid-Crustal Ramp in Kumaun-Garhwal, Central Himalaya: Implications for Regional Tectonics and Seismic Hazard.

Kumar P, Gahalaut VK, Ghosh A.

TECTONICS

https://doi.org/10.1029/2025TC008855 

The Himalayan arc exhibits considerable variation along its strike. It is evident in the current deformation pattern and in earthquake occurrence. This was explored in the Garhwal Kumaun region by analysing the influence of subsurface fault geometry. The Garhwal region accommodates a slightly higher convergence rate and exhibits a gently dipping, wider mid-crustal ramp than the Kumaunsegment.

A prominent lateral ramp, causing megathrust segmentation, is located between the Garhwal and Kumaun Himalaya, which can hinder the propagation of earthquake ruptures. The wider decoupling zone in Garhwal suggests a larger recurrence interval between great earthquakes. The Kumaun megathrust can display seismic quiescence between through‐going ruptures, most likely nucleating at the updip edge of the mid‐crustal ramp.

A schematic representation of the megathrust geometry variations in the Kumaun‐Garhwal region. The approximate boundary between the Garhwal and Kumaun megathrust segments is highlighted. Side perspective view of the megathrust geometry variations in the Kumaun‐Garhwal region, with the locations of the frontal and lateral ramps highlighted in the enlarged circles.

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