Fast slip-rate along the northern end of the Karakorum fault system, western Tibet

Abstract

The exact location of the northern Karakorum fault (KF) in western Tibet is unclear and its current activity is debated. Here, we investigate the possible northern extension of the KF, the Muji fault, located in the Chinese Pamir, which belongs to the Kongur Shan extensional system, and provide the first quantitative estimate of its Holocene slip‐rate. The fault cuts and offsets a series of 6 fluvial terraces, yielding a minimum slip‐rate of 4.5 ± 0.2 mm/yr, by matching the largest terrace riser offset with its upper surface age (10Be, n = 24). Field evidences of right‐lateral movement along the Kongur Shan fault, as well as geometry and kinematic similarities with the southern half of the KF attest that the Muji fault belongs to the KF system. Therefore, its fast slip‐rate combined with the slow slip‐rates along minor splays of the northern KF (maybe up to 4 mm/yr) southwest of the Tashkorgan basin agrees with the late Pleistocene southern KF slip‐rate (>8 mm/yr).

No late Quaternary strike-slip motion along the northern Karakoram fault

“…Additionally, the Dabudar glacial stage deposits that show no lateral separation where they overlie the Achiehkopai fault strand indicate that neither strand of the northern Karakoram fault has carried detectable slip for ∼200 ka or longer. While this interpretation is not as robust as for the Hangdi glacial stage deposits given the highly eroded nature of the Dabudar glacial deposits, Dabudar glacial stage landforms would be expected to show 1-2 km of lateral offset for slip rates of 5-10 mm/yr (Chevalier et al, 2011(Chevalier et al, , 2005, which they clearly do not. Further, the truncation of the topographic scarps in the Dabudar glacial stage deposits by the Tashkorgan glacial stage deposits show they are older than 65 ka, regardless of their origin.…”

“…Several studies of offset geomorphic features have proposed relatively rapid Quaternary slip rates on the Karakoram fault of 7-12 mm/yr along the entire trace of the fault from southeast Tibet to the Pamir (Fig. 1B) (Chevalier et al, 2011(Chevalier et al, , 2005(Chevalier et al, , 2012. Other studies yield considerably slower Quaternary slip rates along the southern portion of the fault system (∼4 mm/yr; Brown et al, 2002Brown et al, , 2005, or have suggested that the northern portion of the Karakoram fault has been inactive during the Quaternary (Robinson, 2009a) with active extension along the Kongur Shan extensional system unrelated to slip on the Karakoram fault (Robinson et al, 2004(Robinson et al, , 2007.…”

“…Recent work based on interpretation of satellite images suggests that the northern end of the Karakoram fault (where it enters the Pamir) has not been active since at least the late Quaternary (Robinson, 2009a), while a study along the Muji segment of the Kongur Shan extensional system to the north suggests the entire Karakoram fault is active with a slip rate of ∼10 mm/yr (Chevalier et al, 2011). Here we report direct field observations coupled with new and previously published geochronologic results along the southern Tashkorgan valley that show the northern portion of the Karakoram fault has not accommodated any detectable slip in the late Quaternary.…”

“…B) Map of the Karakoram fault system showing the trace of the Karakoram and related faults, and documented active structures in western Tibet, and locations of several GPS stations in the Southern Pamir (from Ischuk et al, 2013;Zhang et al, 2004). Numbered locations denote previous studies cited in text: (1) Chevalier et al (2011); (2) Brown et al (2002);…”

Slip Model for the 25 November 2016 Mw 6.6 Aketao Earthquake, Western China, Revealed by Sentinel-1 and ALOS-2 Observations

“…Satellite remotely sensed images and stream terrace studies show that the Muji fault is a dextral strike-slip structure [7,20]. Based on the cosmogenic nuclide dating method, Chevalier et al [21] revealed that the right-lateral slip rate along the Muji fault is 4.5-11 mm/year, and the lithology of the footwall is characterized by mixed Paleozoic metamorphic [7]. As seen from Figure 1, in the Tien Shan and Pamir regions, the GPS-inferred crustal movement velocity exhibits a substantial decreasing trend from the south to north, a well-documented rapid crustal shortening phenomenon, characterized by features of the widespread active faulting and folding, as well as the recent crustal arching and high regional seismicity [22].…”