The Relationship Between Post-Little-Ice-Age Isostatic Rebound and Active Tectonics in Southern Alaska

阿拉斯加南部后小冰期均衡回弹与活动构造的关系

• 批准号: 0408801
• 负责人: Christopher Larsen
• 金额: $ 37.14万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408801&HistoricalAwards=false
• 关键词: Relationship; Between; Post; Little; Ice

This study is determining the relationships between glacial rebound and tectonic strain in southern Alaska. Very high uplift rates (25-30 mm/yr based on GPS) are reported in the region where the Queen Charlotte-Fairweather fault system ends. High horizontal velocities are associated with this transform system and the area has experienced rapid deglaciation since the Little Ice Age. Numerical isostatic rebound models are being used to generate three-dimensional predictions of deformation, which will be constrained by the extensive data set that has already been acquired. This existing data set is the product of an interdisciplinary effort to determine the timing, magnitude and history of uplift and ice load changes in southeast Alaska. The observations consist of a regional Global Positioning System (GPS) crustal deformation array of 76 sites, sea level rates at 18 tide gauge sites, raised shoreline measurements of total uplift, and onset of uplift at 27 sites. These data characterize the regional pattern of uplift on centennial, decadal, and annual time scales, and portray the current regional pattern of three-dimensional crustal deformation. The research team is: 1) refining current glacial isostatic rebound models using an improved GPS and raised shoreline database; 2) developing numerical rebound models that generate three-dimensional predictions of deformation; 3) using model predictions of three-dimensional deformation to remove the horizontal component of isostatically induced motion from horizontal velocity observations to obtain the tectonic deformation of the region; 4) evaluating the resulting tectonic velocity and strain fields in terms of regional crustal dynamics and processes with specific emphasis on the implications for formation of the Fairweather and St. Elias Ranges, genesis of the Denali fault, and dynamics of the Yakutat Block collision; 5) evaluating seismic potential specifically induced by unloading, as well as effects of unloading on tectonic seismic potential. Using numerical models to quantify glacial isostatic rebound, crustal and mantle viscoelastic properties will be resolved using the vertical deformation signal, and thereby provide a means to separate tectonic and isostatic signals in the horizontal deformation field.

这项研究正在确定阿拉斯加南部冰川反弹和构造应变之间的关系。在夏洛特皇后-费尔韦瑟断层系统结束的地区，报告了非常高的抬升速率（根据GPS，25-30毫米/年）。高水平速度与这个转换系统和该地区经历了快速的冰川消退以来的小冰期。数值均衡回弹模型正被用于生成三维变形预测，这将受到已经获得的大量数据集的限制。这个现有的数据集是跨学科努力的产物，以确定阿拉斯加东南部隆起和冰负荷变化的时间，幅度和历史。观测包括一个由76个地点组成的区域全球定位系统地壳形变阵列、18个验潮站的海平面率、总隆起的海岸线隆起测量值以及27个地点的隆起开始。这些数据描述了百年、十年和年时间尺度上的区域隆升模式，并描绘了当前区域三维地壳变形模式。研究团队是：1）使用改进的GPS和升高的海岸线数据库改进当前的冰川均衡回弹模型; 2）开发产生三维变形预测的数值回弹模型; 3）使用三维变形的模型预测从水平速度观测中去除均衡引起的运动的水平分量，以获得该地区的构造变形; 4）根据区域地壳动力学和过程评估由此产生的构造速度场和应变场，特别强调费尔韦瑟山脉和圣埃利亚斯山脉的形成、德纳里断层的成因以及雅库塔特地块碰撞的动力学;（5）评价卸荷引起的地震势及其对构造地震势的影响。利用数值模型量化冰川均衡反弹，地壳和地幔的粘弹性将解决垂直形变信号，从而提供了一种手段，以分离构造和均衡信号在水平形变场。