Evolution and dynamics of a fold-thrust belt: The Sulaiman Range of Pakistan

We present observations and models of the Sulaiman Range of western Pakistan that shed new light on the evolution and deformation of fold-thrust belts. Earthquake source inversions show that the seismic deformation in the range is concentrated in the thick pile of sediments overlying the underthrusting lithosphere of the Indian subcontinent. The slip vectors of the earthquakes vary in strike around the margin of the range, in tandem with the shape of the topography, suggesting that gravitational driving forces arising from the topography play an important role in governing the deformation of the region. Numerical models suggest that the active deformation, and the extreme plan-view curvature of the range, are governed by the presence of weak sediments in a pre-existing basin on the underthrusting Indian Plate. These sediments affect the stress-state in the over-riding mountain range and allow for the rapid propagation of the nose of the range and the development of extreme curvature and laterally varying surface gradients.This study forms part of the NERC- and ESRC-funded project ‘Earthquakes Without Frontiers’. Our thanks go to Jerome Neufeld for many interesting coffee-time discussions, and James Jackson and Dan McKenzie, for comments on the manuscript. We thank Chris Morley and one anonymous reviewer for helpful comments on the manuscript.This article has been accepted for publication in in Geophysical Journal International ©: (2015) 201(2): 683-710, doi: 10.1093/gji/ggv005 , First published online March 9, 2015, Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved