Research Paper GEOSPHERE Late Quaternary slip rate of the Aksay segment and its rapidly decreasing gradient along the Altyn Tagh fault 1,2 1,2 3,4 2 3,4 5 GEOSPHERE, v. 16, no. 6 Jinrui Liu , Zhikun Ren , Wenjun Zheng , Wei Min , Zhigang Li , and Gang Zheng 1State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China 2Key Laboratory of Seismic and Volcanic Hazards, China Earthquake Administration, Beijing 100029, China https://doi.org/10.1130/GES02250.1 3Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China 4Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China 15 figures; 4 tables; 1 supplemental file 5GNSS Research Center, Wuhan University, Wuhan 430079, China CORRESPONDENCE: [email protected]; 2007; Molnar and Dayem, 2010; Royden et al., 2008; and deformation pattern are critical to understand- [email protected] ABSTRACT Tapponnier et al., 2001). Meanwhile, the fault slip ing the mechanics of intracontinental deformation. CITATION: Liu, J., Ren, Z., Zheng, W., Min, W., Li, Z., Constraining the fault slip rate on a fault can rate pattern along strike is also helpful for under- Several researchers have suggested that a decreas- and Zheng, G., 2020, Late Quaternary slip rate of the reveal the strain accumulation and partitioning standing the strain accumulation pattern, fault slip ing trend in the slip rate can be roughly obtained Aksay segment and its rapidly decreasing gradient pattern. The Aksay segment, the eastern segment history, and the strain adjustment and its influence in the east segment of the Altyn Tagh fault from along the Altyn Tagh fault: Geosphere, v. 16, no. 6, p. 1538– 1557, https://doi.org/10.1130/GES02250.1. of the Altyn Tagh fault, as the starting area where on adjacent faults or structures (Resor et al., 2018; these constraints (Zhang et al., 2007; Zheng et al., the slip rate of the Altyn Tagh fault decreases, is a Zechar and Frankel, 2009). A decreasing pattern of 2013). Although previous studies have shown that Science Editor: Andrea Hampel strain partitioning zone. The spatial and temporal slip rates has been widely observed along the typ- the slip rate begins to decrease from the Aksay Associate Editor: Francesco Mazzarini distribution of its fault slip rate is of great signif- ical strike-slip faults around the world, such as the segment (Xu et al., 2005; Zhang et al., 2007), it is icance to clarify the strain-partitioning pattern of Altyn Tagh (Gold et al., 2009; Zhang et al., 2007; still unclear whether the slip rate decreases with a Received 28 February 2020 the eastern Altyn Tagh fault. In this study, we deter- Zheng et al., 2013), Kunlun (Kirby et al., 2007; Lin uniform gradient. Revision received 25 July 2020 Accepted 27 August 2020 mined the slip rates at four sites along the Aksay and Guo, 2008), and North Anatolian fault zones Therefore, we focused on the ~60-km-long Aksay segment. The results demonstrated that the slip (Walters et al., 2014). For instance, a rapid decrease segment in order to systematically constrain the Published online 15 October 2020 rate decreases dramatically, with an overwhelm- in the slip rate of the Haiyuan fault occurs at ~106°E late Quaternary slip rates on the eastern segment ingly high slip gradient of ~9.8 mm/yr/100 km (a in the Madongshan-Liupanshan region, where the of the Altyn Tagh fault based on multilevel displaced 9.8 mm/yr reduction of slip rate occurs over a dis- deformation is dominated by reverse faulting, fold- river terraces at four sites. The initial decrease in the tance of 100 km) within a distance of ~50 km. The ing, and the uplift of regional structures (Li et al., slip rate on the eastern Altyn Tagh fault and multi- slip rate gradient along strike at the Aksay seg- 2009; Zheng et al., 2013). Similarly, the uplift of level offset geomorphic markers could be used ment is four times that of the Subei segment to the the Anyemaqen Shan and the clockwise rotation to constrain more reliable slip rates on the Aksay eastward termination of the Altyn Tagh fault. Our of eastern Kunlun faults accommodated the slip segment. Along this segment, the West of Aksay, results indicate that the slip rate gradient along the rate along the Kunlun fault during structural thick- Old Aksay, Jiaerwuzongcun, and Yandantu sites Altyn Tagh fault is not uniform and decreases east- ening (Kirby and Harkins, 2013). (Fig. 2), from west to east, were investigated both ward with variable slip rate gradients on different The Altyn Tagh fault, as a large-scale boundary in the field and by applying a Monte Carlo analy- segments, resulting in the uplift of the mountains fault between the Tarim block to the north and the sis method. Combined with local geodetic results, oblique to the Altyn Tagh fault. Tibetan Plateau to the south, plays an important we determined the kinematic model of the Aksay role in affecting, and even controlling, the evolution segment, and we discuss its role in the strain par- of the Tibetan Plateau during its NE growth (Molnar titioning of the eastern Altyn Tagh fault here. ■ INTRODUCTION and Rajagopalan, 2012; Tapponnier et al., 2001; Yuan et al., 2013). Studies on temporal and spatial distri- Large active faults in the interior and boundary butions of the slip rate along the Altyn Tagh fault are ■ GEOLOGICAL BACKGROUND of a plateau can provide kinematic constraints for essential for understanding the tectonic evolution fault interactions and rupture dynamics, which is of of the northern Tibetan Plateau. With a series of Qilian Shan great significance to understanding the strain par- mountains oblique to the fault (Fig. 1), the eastern titioning and seismic hazard assessment (Meade, segment of the Altyn Tagh fault is a very important The Qilian Shan (Shan = Mountains), located This paper is published under the terms of the strain partitioning zone on the northeastern Tibetan on the northeastern margin of the Tibetan Plateau CC-BY-NC license. Zhikun Ren https://orcid.org/0000-0002-6391-9503 Plateau. The strike-slip rate gradients along the fault (Fig. 1), has experienced intensive deformation © 2020 The Authors GEOSPHERE | Volume 16 | Number 6 Liu et al. | Slip rate of the Aksay segment and its rapidly decreasing gradient along the Altyn Tagh fault Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/16/6/1538/5183017/1538.pdf 1538 by guest on 26 September 2021 Research Paper B 90°E 95°E 100°E Gobi-Alashan 9 Tarim 8 1 6 Jiuxi Basin Figure 2 1 Hexi Corridor 3 4 7 6 1 Daxue Shan Qilian Shan 39°N 5 Danghe Nan Shan 4 5 3 2 3 4 2 1 Haiyuan Fault Qaidam Figure 1. Tectonic setting of study area. 1 Altyn Tagh Fault (A) Tectonic map of the Tibetan Plateau 85°E 90°E 95°E 100°E 105°E (from Tapponnier et al., 2001). (B) Ge- 40°N A ometry and locations of slip rates from previous studies along Altyn Tagh fault 36°N Figure 1B 35°N (ATF), based on the Shuttle Radar Topog- Kunlun Fault Tibetan Plateau raphy Mission data with 90 m resolution. 30°N The locations of the active fault traces 0 100 200 0 500 1000 follow Deng et al. (2003). Seismic data 85°E km 90°E 95°E 40-50mm/yr km 25°N are from the China Earthquake Infor- 7 Geological Study Chen et al., 2012; InSAR Study Historical Earthquakes mation Network (2020). GPS—global Chen et al., 2013 1 Zhang et al., 2007 Ms=8.0-8.9 positioning system; InSAR—interfero- 8 Kang et al, 2019 Jolivet et al., 2008 2 Cowgill, 2007; Ms=7.0-7.9 metric synthetic aperture radar. 9 Zhang, 2016 Cowgill et al., 2009 Liu et al., 2018a Ms=6.0-6.9 3 Gold et al, 2009; GPS Study Bendick et al., 2000 Ms=5.0-5.9 Gold and Cowgill, 2011 Altyn Tagh Fault 4 Meriaux et al., 2004; Shen et al., 2001 Elevation (m) Meriaux et al., 2005; 7000 Wallace et al., 2004 Main Strike-slip Faults Meriaux et al., 2012 Zhang et al., 2007 5000 5 Washburn et al., 2001; He et al., 2013 Thrust Faults Washburn et al., 2003 2000 Zheng et al., 2017 Other Faults 6 Xu et al., 2005 Li et al., 2018 0 since the late Cenozoic related to the northeast- Shan and the Altyn Tagh fault. Previous research lithosphere scale in the Eurasian plate (Fig. 1; Mol- ward growth of the plateau (Meyer et al., 1998; proposed that the subparallel Cenozoic thrust nar and Tapponnier, 1975; Tapponnier et al., 1982, Zhang et al., 2004; Duvall et al., 2013; Yuan et al., branches southeastward from the Altyn Tagh fault 2001; Yin et al., 2002; Xu et al., 2005; Zhang et al., 2013; Allen et al., 2017). Due to the NE-SW regional absorbed the crustal shortening along these struc- 2007). Studying its temporal and spatial distribu- stress induced by plate motion, the strain in the tures (Meyer et al., 1998; Van der Woerd et al., 2001). tions of slip rates is essential to reveal the pattern of Qilian area is partitioned into dip-slip and strike-slip However, Allen et al. (2017) suggested that the Qil- northeastward growth of the Tibetan Plateau (Meyer components (Allen et al., 2017). The strike-slip struc- ian thrust was not a secondary feature caused by et al., 1998; Cunningham et al., 2016). tures are mainly large-scale strike-slip faults, such the activity of Altyn Tagh fault, but a major part of The long-term average slip rates over millions as the Altyn Tagh fault and Haiyuan fault.