Tajik Depression and Greater Pamir Neotectonics from InSAR Rate Maps

Embedded between the Tian Shan, Pamir, and Hindu Kush, the Tajik depression is a remnant of the Mesozoic-Miocene Tajik-Tarim basin system. Since ~12 Ma, westward collapse of the north-advancing Pamir-Plateau crust inverted the Tajik basin into a thin-skinned fold-thrust belt with ~150 km of ~E-W shortening distributed between foreland- and hinterland-vergent structures. Geodetically-derived shortening rates decay westward from ~15 to 2 mm/yr. Seismicity outlines the ~east-striking dextral Ilyak fault, bounding the fold-thrust belt in the north, and distributed shortening in the central and eastern Tajik depression. We derived E-W and vertical deformation-rate maps from radar interferometric time-series, consisting of 900+ radar scenes acquired over 2.0-4.5 years, and available accurate positioning data. We confirm the westward collapse of the Pamir and the drastic shortening-rate decline across the Main Pamir Thrust at the Pamir front. In the Tajik depression, the maps unveil a combination of basin-scale tectonics, local halokinesis, and seasonal/weather-driven soil or near-surface effects. Although the Tajik-basin strata move westward with rates decreasing away from the Pamir, the most external Babatag backthrust currently absorbs the highest shortening (~6 mm/yr) as it has done in the past (>20 km). The Ilyak fault accommodates ~5-8 mm/yr, eastward-increasing slip; rates decay sharply across the fault, suggesting a locking depth of <1 km - possibly creep. At least 10 mm/yr uplift and westward motion occur across the Tajik-depression-Pamir transition, including the sinistral Darvaz fault zone, likely outlining a crustal-scale ramp. The Hoja Mumin salt fountain is spreading laterally at >300 mm/yr.