Evolution of the Karakorum Fault: Propagation and Abandonment along An Intercontinental Strike-Slip Fault

The Karakorum fault bounds the western margin of the Tibetan plateau, running for >1000 km from the Himalayas to the central Pamir. Unlike other major strike-slip faults in the Indo-Asian collision zone, the Karakorum fault cuts across the elevated topography and tectonic terranes of the Tibetan orogen rather than along or parallel to major discontinuities in crustal properties within the collision zone (e.g. the Altyn Tagh fault). Two observations indicate major changes in the role and trace of the fault during its evolution: 1) The Karakorum fault exhibits a large decrease in magnitude of slip from the northern portion north of the Bangong-Nujiang suture where it has accommodated ~150 km of slip, to the southern half where it has accommodated ~65 km of slip. This change in displacement has been interpreted to indicate the fault evolved over time, initially acting as a transfer structure linking thrust belts in the Pamir and western Tibet, then propagating southward to accommodate oroclinal bending of the Himalayan arc (Murphy et al., 2000). 2) The northern portion of the fault does not appear to have been recently active, possibly due to cessation of major shortening in the Pamir and western Tibet and/or impingement from the Longmu Co-Gozha Co fault (Raterman et al., 2006). Thus the Karakorum fault appears to be an example of an intercontinental strike-slip fault which, in addition to changing the role it plays in accommodating regional deformation, has abandoned its original portion while still accommodating strain along strike where it propagated . This model suggests that large strike-slip faults which are embedded within orogenic belts are both unstable as well as highly dynamic structures over millions of years.