Tectonic highlights of the recent deformation field of the Pamir, the Tajik basin, and the Hindu Kush, observed by high-resolution satellite-geodesy
Authors: Metzger Sabrina , Gągała Łukasz , Kakar Najibullah , Ratschbacher Lothar , Zubovich Alexander , Kley Jonas , Schöne Tilo , Schurr Bernd , Lazecký Milan , Maghsoudi Yasser , Zech Cornelia , Moldobekov Bolot , Sharshebaev Azamat 
Published: March 2022

&lt;p&gt;&lt;span&gt;At the northwestern tip of the India-Asia collision zone, the north-advancing Pamir orocline overrides the Tajik-Tarim Basin &lt;/span&gt;&lt;span&gt;along a low-angle &lt;/span&gt;d&amp;#233;collement with N&amp;#8211;S shortening rates of 10-15 mm/yr. The Pamir&amp;#8217;s advance is buttressed in the North by the&lt;span&gt; Tian Shan. Westward collapse of Pamir crust into the Tajik basin leads to overall E&amp;#8211;W shortening in the ~N-trending Tajik fold-thrust-belt. Crustal seismicity highlights fault systems at the northern rim of the Pamir and, since the 2017 M&lt;/span&gt;&lt;sub&gt;&lt;span&gt;w&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;7.2 Sarez earthquake, the Sarez-Karakul fault system that separates the &lt;/span&gt;&lt;span&gt;western&lt;/span&gt;&lt;span&gt; from the &lt;/span&gt;&lt;span&gt;eastern&lt;/span&gt;&lt;span&gt; Pamir as a surface expression of the northwestern tip of the &lt;/span&gt;&lt;span&gt;underthrusting&lt;/span&gt;&lt;span&gt; Indian craton&lt;/span&gt;&lt;span&gt;ic mantle lithosphere&lt;/span&gt;&lt;span&gt;. Towards southwest, the Pamir connects to the rarely sampled Hindu Kush with sparse crustal but abundant intermediate-depth seismicity; &lt;/span&gt;&lt;span&gt;the latter is an effect on&lt;/span&gt;&lt;span&gt; an ongoing slab break-off.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;We &lt;/span&gt;&lt;span&gt;recorded displacements along&lt;/span&gt;&lt;span&gt; the most active structures creating the recent regional deformation field &lt;/span&gt;&lt;span&gt;by&lt;/span&gt;&lt;span&gt; multiple satellite-geodetic observations. &lt;/span&gt;&lt;span&gt;Up to &lt;/span&gt;&lt;span&gt;4.5-yr-long radar-interferometric time-series (InSAR) provide E&amp;#8211;W and vertical surface deformation field&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt; in unprecedented spatio-temporal resolution of 400 m &lt;/span&gt;&lt;span&gt;and&lt;/span&gt;&lt;span&gt; 12-24 days. The relative InSAR rate maps were tied to and complemented with accurate rates derived from Global Navigation Satellite System (GNSS) data. &lt;/span&gt;&lt;span&gt;We collected these data&lt;/span&gt;&lt;span&gt; in continuous and survey mode along&amp;#8212;sometimes km-spaced&amp;#8212;profiles across the most active faults in the region.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;We confirm the high interseismic strain localization along the Pamir&amp;#8217;s northern &lt;/span&gt;&lt;span&gt;thrust&lt;/span&gt;&lt;span&gt; front and an increased dextral component towards the northwestern edge of the &lt;/span&gt;&lt;span&gt;thrust belt&lt;/span&gt;&lt;span&gt; of &gt;8 mm/yr, accommodat&lt;/span&gt;&lt;span&gt;ing&lt;/span&gt;&lt;span&gt; the westward collapse of the orocline. The sinistral Sarez earthquake &lt;/span&gt;&lt;span&gt;at 120-170 km distance &lt;/span&gt;&lt;span&gt;from the front&lt;/span&gt;&lt;span&gt; activated the basal d&lt;/span&gt;&lt;span&gt;&amp;#233;collement, as suggested by mm-&lt;/span&gt;&lt;span&gt;to-cm-scale, sharp surface offsets along the whole frontal segment. Relocking occurred gradually in the following four years. Similar co-seismic offsets were observed a&lt;/span&gt;&lt;span&gt;long&lt;/span&gt;&lt;span&gt; the sinistral, NE-trending Darvaz fault, separating the &lt;/span&gt;&lt;span&gt;western&lt;/span&gt;&lt;span&gt; Pamir from the Tajik basin. The Tajik fold-thrust-belt exhibits ~10 mm/yr of internal E&amp;#8211;W shortening, in agreement with fossil shortening rates of 12-8 mm/yr &lt;/span&gt;&lt;span&gt;since ~12 Ma. The majo&lt;/span&gt;&lt;span&gt;rity of the deformation is accommodated by the Babadag backthrust (~6 mm/yr)&amp;#8212;a major thrust located far west in the belt, and the sinistral &lt;/span&gt;&lt;span&gt;Ilyak&lt;/span&gt;&lt;span&gt; fault (~6 mm/yr) that bounds the belt to the North. The belt also hosts spectacular &lt;/span&gt;&lt;span&gt;horizontal &lt;/span&gt;&lt;span&gt;spreading rates of &lt;/span&gt;&lt;span&gt;&amp;#8804;&lt;/span&gt;&lt;span&gt;350 mm/yr at the Hoja Mumin salt fountain. A&lt;/span&gt;&lt;span&gt;long&lt;/span&gt;&lt;span&gt; the most prominent fault of the Hindu Kush, the Panjsheer fault, a fault-perpendicular GNSS profile &lt;/span&gt;&lt;span&gt;observed&lt;/span&gt;&lt;span&gt; sinistral slip of &gt;1-4 mm/yr. The fault is probably only locked in the upper &lt;/span&gt;&lt;span&gt;~km &lt;/span&gt;&lt;span&gt;as &lt;/span&gt;&lt;span&gt;suggested by&lt;/span&gt;&lt;span&gt; a sharp, InSAR line-of-sight rate increase of ~6 mm/yr across the fault. This could explain the absence of shallow seismicity in the region.&lt;/span&gt;&lt;/p&gt;