PRELIMINARY ASSESSMENT OF QUATERNARY FAULTING IN AFGHANISTAN

The USGS is constructing a Quaternary fault map of Afghanistan to be used for future seismic hazard analyses and individual fault studies. Faults are identified and mapped using 14.25 m resolution Landsat imagery that merges bands 731 and 741 for natural color imagery. Recognition and characterization of faults are based on offset Quaternary landforms primarily within valleys and along mountain-piedmont junctions. Fault expression in alpine regions is predominantly limited to bedrock fault scarps and lineaments.

The Transpressional Plate Boundary region of eastern Afghanistan is characterized by active strike-slip and thrust faults. The Chaman, Gardez, Paghman, and Konar are left-lateral srike-slip faults characterized by large, multiple-event, continuous fault scarps on late Quaternary deposits. The Sulaimon fold and thrust belt consists of numerous discontinuous, arcuate and continuous, linear fault scarps that mark the traces of active imbricate thrusts, lateral ramps and tear faults.

The North Afghan Platform, north of the Hari Rod fault, is characterized by an E-W-trending structural grain with right-lateral fault zones. The Hari Rod fault shows little evidence for Quaternary activity west of its junction with the Paghman fault. The Andarab and Dosi Mirzavalen faults to the north are marked by continuous right-lateral fault scarps. Further to the north, fault zones with discontinuous, right-lateral fault scarps on late Quaternary deposits, suggest a northward migration of right-lateral shear. The Alburz-Marmul fault is marked by discontinuous fault scarps with right-lateral and oblique thrust displacement that bound a large, active NNE-trending pressure ridge to the south.

The Accreted Terranes province of southwest Afghanistan displays structural control of local drainage in late Quaternary deposits of the Helmand basin. Evidence of faulting is also expressed by uplifted and incised fan surfaces and discontinuous fault scarps.