Geodynamic modelling of subduction beneath the Pamir-Hindu Kush region

Seismic tomography indicates that the Pamir-Hindu Kush, the northwestern margin of India-Asia collision zone, has unique distinguished subducting characteristics. A map of seismicity in this area suggests a north-dipping and southeast-dipping structure in Hindu Kush and Pamir, respectively. The India lithosphere slab is subducting beneath Asia in Hindu Kush, while the Asia lithosphere is subducting under the Pamir. Kufner et. al.(2016) proposed that the different rheology and thickness of India plate causes the change in polarity of the subduction zone as show in the earthquake catalogue and tomography image below..

To test this hypothesis , we construct 2D numerical models of subduction using ASPECT (Advanced Solver for Problems in Earth's ConvecTion).Model 1 is a 2D subduction calculation simulating the Indian plate subducting beneath the Asian plate. Model 2 simulates the detaching of a weak Indian slab which occurs during collision, causing the Asian lithosphere to subduct beneath Pamir. We vary the rheology and thickness of the Indian plate to determine under what conditions the detaching of the Indian slab will occur.

Figure a). Map showing location and topography of Pamir-Hindu Kush region (Negredo et al., 2007). b). Earthquake catalogue of Pamir and Hindu Kush (Kufner et al., 2016). c-e). Cross-sections of P-wave tomography model (Negredo et al., 2007).