Kinematics and dynamics of the Pamir, Central Asia: Quantifying surface deformation and force balance in an intracontinental subduction zone

Kinematic and dynamic models quantify deformation and force balance in the Pamir, a region undergoing the rare and poorly understood process of intracontinental subduction. We constrain a detailed kinematic model with 506 recent GPS velocities and Quaternary fault slip rates and show that the Pamir is organized like the Himalaya and Tibet, with regions of (1) localized strain rate ≥100e-9/year along the Pamir Frontal Thrust System (the subduction interface), similar to the Himalaya, and (2) distributed north-south compression and east-west extension, similar to Tibet. Through standard thin viscous sheet methods we demonstrate that the lithospheric force balance in the Pamir is a combination of stresses caused by gravitational potential energy and India-Eurasia convergence accommodated at a subduction interface, in this case the Pamir Frontal Thrust System. We find that strain rate and deviatoric stress patterns near the Pamir Frontal Thrust System are characteristic of a mature subduction zone, despite its initiation in continental lithosphere. Although the Pamir and Tibet are kinematically and dynamically similar, the Pamir is stiffer overall than Tibet, perhaps due to the presence of the highly arcuate, geometrically stiffened continental slab at depth.