Abstract
AbstractUsing E‐W and vertical deformation‐rate maps derived from radar interferometric time‐series, we analyze the deformation field of an entire orogenic segment, that is, the Tajik depression and its adjoining mountain belts, Tian Shan, Pamir, and Hindu Kush. The data‐base consists of 900+ radar scenes acquired over 2.0–4.5 years and global navigation satellite system measurements. The recent, supra‐regional kinematics is visualized in an unprecedented spatio‐temporal resolution. We confirm the westward collapse of the Pamir‐Plateau crust, inverting the Tajik basin into a fold‐thrust belt (FTB) with shortening rates decaying westward from ∼15 to 2 mm/yr. Vertical rates in the Hindu Kush likely record slab‐dynamic effects, that is, the progressive break‐off of the Hindu Kush slab. At least 10 mm/yr of each, uplift and westward motion occur along the western edge of the Pamir Plateau, outlining the crustal‐scale ramp along which the Pamir Plateau overrides the Tajik depression. The latter shows a combination of basin‐scale tectonics, halokinesis, and seasonal/weather‐driven near‐surface effects. Abrupt ∼6 mm/yr horizontal‐rate changes occur across the kinematically linked dextral Ilyak strike‐slip fault, bounding the Tajik FTB to the north, and the Babatag backthrust, the major thrust of the FTB, located far west in the belt. The sharp rate decay across the Ilyak fault indicates a locking depth of ≤1 km. The Hoja Mumin salt fountain is spreading laterally at ≤350 mm/yr. On the first‐order, the modern 20–5 and fossil (since ∼12 Ma) 12–8 mm/yr shortening rates across the FTB correspond.
Highlights
At the western end of the India-Asian collision zone, the Tian Shan, Pamir, and Hindu Kush frame the Tajik depression, hosting the Tajik basin (Figure 1a)
The distribution and age of deformation is known geologically, the relative short observation period used to record seismicity by high-resolution temporary networks (Kufner et al, 2018; Schurr et al, 2014), the sparse GNSS data (e.g., Ischuk et al, 2013; Metzger et al, 2020), and the paucity of detailed neotectonic observations (Trifonov, 1978) limit the quantification of how far the deformation field of the Pamir is influencing the Tajik depression and how the individual structures in the fold-thrust belt (FTB) are contributing to its active shortening
We overcame this to some extent by tying the rates to the GNSS reference frame, but some sharp jumps along frame boundaries remain; these are in the Afghan platform, the western Ferghana depression, the Dushanbe trough north of the Ilyak fault, and the upper Panj-river valley
Summary
East- and up-rate maps exhibit tectonic and anthropogenic processes with mm-accuracy in high spatial resolution (400 m). Rate map quality depends on interferometric data coherence and the availability of stabilizing Global Navigation Satellite System data. Major tectonic signal is E–W shortening in the Tajik fold-thrust belt due to the westward collapse of the Pamir-Plateau crust. Supporting Information: Supporting Information may be found in the online version of this article. Sabrina Metzger , Łukasz Gągała2,3 , Lothar Ratschbacher , Milan Lazecký , Yasser Maghsoudi , and Bernd Schurr
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