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

合作研究：阿尔金断裂带全新世滑移率是10毫米/年、30毫米/年还是两者？

• 批准号: 0610107
• 负责人: Eric Cowgill
• 金额: $ 25.52万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0610107&HistoricalAwards=false
• 关键词: Collaborative; Research; Holocene; Slip; Rate

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.

测量阿尔金断裂带的全新世滑动速率对于促进对大陆内主要断裂系统力学行为的理解以及区分亚洲地壳和岩石圈相互冲突的流变模型至关重要。先前的工作得出了断层中心部分的两种相互矛盾的滑动速率：GPS和古地震学研究给出了0.01至2-3千年前的滑动速率约为10毫米/年，而地貌重建得出的结果是6至11.3万年前的滑动速率约为30毫米/年。在2000年至6000年前的滑动率数据中存在一个重要的时间差距，这可以用以下方式来解释：(1)滑动率在几千年里变化了三倍；(2)时间滑移率恒定且缓慢（约10 mm/yr）；或(3)恒定且快速（约30mm/yr）的时间滑移率。这项为期三年的综合古地震和滑动率研究将沿着阿尔金塔赫断层的中央进行，将区分这三种假设的滑动历史，为2至6千年的间隙。古地震学研究描述了最近地表破裂的大小、年龄、偏移和震级。滑移率是通过在六个新地点重建移位的河流阶地上升台来确定的。利用放射性碳、光激发发光和共源放射性核素方法，对移位的河流阶地进行了测量和定年。沿着阿尔金断裂带建立全新世滑动历史对于确定亚洲最好被视为微板块拼贴还是薄粘性片是很重要的。Altyn Tagh断层是印度-亚洲碰撞中最大的活动走滑断层，在关于欧亚大陆以及一般大陆的变形行为的长期争论中起着核心作用。这场争论的核心在于断层在过去一万年中移动的速度。这项研究的结果将(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式；(2)为陆内断裂动力学模型提供观测约束；(3)提高对阿尔金断裂带附近人口增长中心地震风险的认识。