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Abstract: The 400km-long Karakax left-lateral strike-slip fault is the westernmost segment of the Altyn Tagh fault. It separates northwestern Tibet to the south from the Tarim basin to the north. The western section of the Karakax fault exhibits clear co-seismic surface ruptures of past large earthquakes. Geomorphic offset measurements from the field and high-resolution Ikonos images along 1.5km across the Sanshiliyingfang fan and along 55km of the fault, range from 3 to 28m, with distinct clusters at 6±2(3), 14±2, 19±2 and 24±3m. The cluster of the smallest offsets around 6m (full range from 3 to 10m) distributed over a minimum length of 55km, is attributed to the last largest surface rupturing event that testifies of the occurrence of a magnitude Mw 7.4–7.6 earthquake along the Karakax fault. We interpret the other offset clusters as the possible repetition of similarly sized events thus favoring a characteristic slip model for the Karakax fault. In a 3m-deep trench dug across the active trace of the fault we can identify the main rupture strands of the last and penultimate events. The penultimate event horizon, a silty-sand layer, has been radiocarbon dated at 975–1020AD (AMS 14C age). It is proposed that large Mw 7.4–7.6 events with co-seismic slip of about 6m rupture the Karakax fault with a return time of about 900years implying an average slip-rate of about 6–7mm/years during the late Holocene. These results suggest that the Karakax fault is the largest left-lateral strike-slip fault at the rim of northwestern Tibet accommodating eastward movement of Tibet due to the India–Eurasia collision. [Copyright &y& Elsevier]

The left-lateral strike-slip Xianshuihe fault system located in the eastern Tibetan Plateau is considered as one of the most tectonically active intra-continental fault system in China, along which more than 20 M > 6.5 and more than 10 M > 7 earthquakes occurred since 1700. Therefore, studying its activity, especially its slip rate at different time scales, is essential to evaluate the regional earthquake hazard. Here, we focus on the central segment of the Xianshuihe fault system, where the Xianshuihe fault near Kangding city splays into three branches: the Selaha, Yalahe and Zheduotang faults. In this paper we use precise dating together with precise field measurements of offsets to re-estimate the slip rate of the fault that was suggested without precise age constraints. We studied three sites where the active Selaha fault cuts and left-laterally offsets moraine crests and levees. We measured horizontal offsets of 96 ± 20 m at Tagong levees (TG), 240 ± 15 m at Selaha moraine (SLH) and 80 ± 5 m at Yangjiagou moraine (YJG). Using 10 Be cosmogenic dating, we determined abandonment ages at Tagong, Selaha and Yangjiagou of 12.5 ( + 2.5 / − 2.2 ) ka, 22 ± 2 ka, and 18 ± 2 ka, respectively. By matching the emplacement age of the moraines or levees with their offsets, we obtain late Quaternary horizontal average slip-rates of 7.6 ( + 2.3 / − 1.9 ) mm/yr at TG and 10.7 ( + 1.3 / − 1.1 ) mm/yr at SLH, i.e., 5.7–12 mm/yr or between 9.6 and 9.9 mm/yr assuming that the slip rate should be constant between the nearby TG and SLH sites. At YJG, we obtain a lower slip rate of 4.4 ± 0.5 mm/yr, most likely because the parallel Zheduotang fault shares the slip rate at this longitude, therefore suggesting a ∼5 mm/yr slip rate along the Zheduotang fault. The ∼10 mm/yr late Quaternary rate along the Xianshuihe fault is higher than that along the Ganzi fault to the NW (6–8 mm/yr). This appears to be linked to the existence of the Longriba fault system that separates the Longmenshan and Bayan Har blocks north of the Xianshuihe fault system. A higher slip rate along the short (∼60 km) and discontinuous Selaha fault compared to that along the long (∼300 km) and linear Ganzi fault suggests a high hazard for a M > 6 earthquake in the Kangding area in the near future, which could devastate that densely populated city. [ABSTRACT FROM AUTHOR]

Southern Tibet is characterized by seven main N-S trending rifts bounded by normal faults which accommodate E -W extension. Quantifying the throw and extension rates along these rifts is essential to understand their activity, onset timing, regional seismic hazard and kinematic role in the tectonic evolution of the Tibetan Plateau. The Yadong-Gulu rift (YGR), near Lhasa, is the longest and most prominent rift in southern Tibet, and one of the few that crosses the Himalayas, however it remains poorly studied and understood. Here, we focus on the Yadong rift, i.e., the southern section of the YGR, south of the Yarlung Zangbo suture. We determine the late Quaternary/Holocene throw rates at four sites, where the active Yadong normal fault vertically offsets glacial and fluvial geomorphic surfaces. Using terrestrial LiDAR, UAV and kinematic GPS, we precisely measured vertical offsets (up to 17 m) and constrained the age of abandoned surfaces using 32 10Be cosmogenic surface-exposure ages (~10–20 ka), one optically stimulated luminescence age and two travertine samples dated using U-series dating. The offset-age reconstructions yield uniform throw rates of 0.9 ± 0.3 mm/yr along the entire Yadong rift. Taking a fault dip of 50° as measured in the field, we obtain late Quaternary E -W extension rates of 0.8 ± 0.3 mm/yr, which is similar to but at the lower end of those along other rifts in southern Tibet (~1–2 mm/yr). • Late Quaternary throw rates are uniform all along the rift at 0.9 ± 0.3 mm/yr. • Extension rate is 0.8 ± 0.3 mm/yr (dip of 50°), slightly lower than along other rifts. • No vertical offsets >17 m exist along the entire rift due to climatic reasons. • Seismic hazard exists in the Yadong rift, especially in the Pagri graben. [ABSTRACT FROM AUTHOR]

The Pamir Salient and Southwestern Tien Shan belong to two different systems, which collided due to the continuous northward drift of the Indian Plate during the Cenozoic, resulting in a shortening of ~ 300 km. The uplift history and kinematic evolution of the Pamir-Southwestern Tien Shan remain unclear. In this study, we chose the 2025 m-thick Pakabulake formation in the East Wuqia section, at the southern-most margin of the Southwestern Tien Shan system, to obtain a high-resolution magnetostratigraphic record spanning ~ 16.61 Ma to ~ 9.78 Ma. Based on its high sedimentation rate, stable ca. E-W paleocurrents and stable magnetic susceptibility values, the nearby Southwestern Tien Shan was inferred to have undergone stable uplift during this period of sedimentation. Combining our results with the previous low-temperature thermochronology, magnetostratigraphy and re-calculated block rotations, we conclude that four episodic uplift events occurred in the Pamir-Southwestern Tien Shan during the Cenozoic, at times of ~ 50–40 Ma, ~ 35–16 Ma, ~ 11–7 Ma and < 5 Ma, and that the first episodic uplift only occurred in the Pamir Salient. In addition, the Pamir Salient underwent a tectonic transformation from entire- to a half-oroclinal bending rotation during the Miocene, caused by activity along the Karakorum Fault and Kashgar-Yecheng Transfer System. [ABSTRACT FROM AUTHOR]

The Litang fault system (LTFS) in the eastern Tibetan Plateau has generated several large (7.5 > M > 7) historical earthquakes and has exhumed granitic peaks rising > 1700 m above the mean elevation of the plateau, despite being located within a tectonic block surrounded by highly active faults. We study horizontally offset moraine crests from the Cuopu basin and a vertically offset alluvio-glacial fan from the eastern Maoya basin. We determine a left-lateral rate of 0.09 ± 0.02 mm/yr along a slowly slipping secondary fault at Cuopu, while the main active fault at present is the normal range-front N Cuopu fault, along which we determined a left-lateral rate of 2.3 ± 0.6 mm/yr since 173 ka. At Maoya fan, matching the vertical 12 ± 1 m cumulative offset with the 21.7 ± 4.2 ka fan age yields a vertical (normal) rate of 0.6 ± 0.1 mm/yr. This rate is very similar to that recently determined at the same location using low-temperature thermochronology (0.59 ± 0.03 mm/yr since 6.6 ± 0.5 Ma). Left-lateral rates along the main faults of the LTFS range between 0.9 and 2.3 mm/yr at all timescales from a few years to ~ 6 Ma. The facts that the LTFS is highly segmented and that at present, the Cuopu, Maoya and South Jawa segments are mostly normal (while the Litang and Dewu segments are left-lateral/normal), could prevent the occurrence of M > 7.5 destructive earthquakes along the LTFS, as is generally assumed. However, motion on the normal faults appears to be linked with motion on the strike–slip faults, potentially allowing for exceptional larger earthquakes, and implying that the area is not experiencing pure ~ NS extension but rather NW–SE left-lateral transtension. [ABSTRACT FROM AUTHOR]