Collaborative Research: Is the Holocene Slip Rate along the Altyn Tagh Fault 10 mm/y, 30 mm/y, or Both? Infilling a 2-6 ka Data Gap Using 14C, OSL, and Stream Reconstructions

阿尔金-塔格活动左滑断裂沿青藏高原西北缘延伸1200多公里，是印亚碰撞中的一级构造。阿尔金断裂全新世滑动速率的测量对于加深对大陆内主要断裂系统的力学行为的认识以及区分相互冲突的亚洲地壳和岩石圈的流变模型都是至关重要的。以前的工作给出了断层中央的两个相互矛盾的滑动速率：GPS和古地震学研究给出了0.01年前和2-3000年前之间大约10毫米/年的滑动速率，而地貌重建在6000年到113 000年前之间的滑动速率大约为30毫米/年。在两千年到六千年前的滑移率数据中存在着一个重要的时间间隔，这可以用以下几个方面来解释：(1)几千年来滑移率变化三倍；(2)时间上滑移率恒定而缓慢(约10毫米/年)；(3)时间上滑移率恒定而快速(约30毫米/年)。这项沿阿尔金断裂中央进行的为期三年的综合古地震和滑动速率研究将区分这三种假想的两千到六千年间的滑动历史。古地震学研究确定了最近地表破裂的大小、年龄、偏移量和震级。滑移率是通过在六个新地点重建置换的河流阶地立管来确定的。移位的河流阶地正在用放射性碳法、光激发发光法和宇宙源放射性核素法进行测量和年代测定。建立沿阿尔金断裂的全新世滑移史对于确定亚洲是微板块的拼贴还是粘性薄片的最佳选择具有重要意义。阿尔金断裂是印度支那-亚洲碰撞中最大的活动走滑断裂，在关于欧亚大陆乃至整个大陆变形行为的长期争论中发挥着核心作用。这场辩论的核心是关于断层在过去1万年中移动的速度的争议。这项调查的结果将(1)解决有争议的滑动速率，并允许区分扩散和局部大陆变形模型；(2)为陆内断裂动力学模型提供观测约束；以及(3)提高对阿尔金断裂附近不断增长的人口中心的地震风险的理解。

The active, left-slip Altyn Tagh Fault extends for over 1200 km along the northwestern margin of the Tibetan Plateau, making it a first-order structure within the Indo-Asian collision. Measuring the Holocene slip rate along the Altyn Tagh Fault is essential for both advancing understanding of the mechanical behavior of major intracontinental fault systems and discriminating between conflicting rheological models of the Asian crust and lithosphere. Previous work has produced two contradictory slip rates for the central portion of the fault: GPS and paleoseismological studies give rates of about 10mm/y between 0.01 and 2-3 thousand years ago whereas geomorphic reconstructions yield rates of approximately 30 mm/yr between 6 and 113 thousand years ago. There is an important temporal gap in slip-rate data between 2 and 6 thousand years ago that may be explained by: (1) slip rate variations by a factor of three over a few thousand years; (2) constant and slow (about 10 mm/yr) slip rate in time; or (3) constant and fast (about 30mm/yr) slip rate in time. This three-year, integrated paleoseismic and slip-rate study along the central Altyn Tagh fault will distinguish between these three hypothesized slip histories for the 2 to 6 thousand year gap. Paleoseismological studies characterize the size, age, offset and magnitude of the most-recent surface-breaking ruptures. Slip rates are determined by reconstructing displaced fluvial terrace risers at six new sites. Displaced fluvial terraces are being measured and dated using radiocarbon, optically stimulated luminescence, and cosmongenic radionuclide methods. Establishing the Holocene slip history along the Altyn Tagh Fault is important for determining if Asia is best viewed as a collage of microplates or a thin viscous sheet.The Altyn Tagh Fault, the largest active strike-slip fault within the Indo-Asian collision, plays a central role in a long-standing debate over the deformational behavior of the Eurasian continent and, by implication, continents in general. At the heart of this debate lies a dispute over the rate at which the fault moved during the last 10,000 years. The results from this investigation will (1) resolve the disputed slip rate and allow distinction between the diffuse and localized continental deformation models; (2) provide observational constraints for models of intracontinental fault dynamics; and (3) improve understanding of the seismic risk to growing population centers near the Altyn Tagh Fault.