Kinematics and Dynamics of the Pamir, Central Asia: Quantifying the Roles of Continental Subduction in Force Balance

Abstract

An updated kinematic model constrained by GPS observations and fault slip rate information from the Central Asia Fault Database provides updated modeled slip rates for major faults in the Pamir. The kinematic model constrains thin sheet continuum mechanics models that distinguish the contributions of subducting continental lithosphere to force balance. Dynamic model sensitivity tests show that major features of the force balance results are insensitive to chosen lithospheric compensation style, integration depth, and inclusion of subducting low-density continental lithosphere in the upper 100 km. Forward models incorporate deviatoric stresses associated with gravitational potential energy, velocity boundary conditions, and lateral strength variations. Differential strain rate fields, which represent residual forces not accounted for in the forward models, separate and quantify the deformation associated with the Pamir slab. The downward pull of foundering lithosphere augments compression along the Pamir Frontal Thrust System and shear along the eastern and western Pamir boundaries. North-south extension in the residual differential strain rate field is spatially associated with Pamir gneiss domes and may be related to the interaction of the slab with the mantle. We do not find evidence for slab pull associated with a separate Hindu Kush slab.