Collaborative Research: An integrated GPS and Structural Study of the Cocos-Caribbean Boundary in Nicaragua and El Salvador

合作研究：尼加拉瓜和萨尔瓦多科科斯-加勒比边界的综合 GPS 和结构研究

• 批准号: 1063247
• 负责人: Glen Mattioli
• 金额: $ 11.95万
• 依托单位: University of Texas at Arlington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1063247&HistoricalAwards=false
• 关键词: Collaborative; Research; integrated; GPS; Structural

In this four year geodetic and structural study of the Cocos-Caribbean convergent margin along the Pacific coasts of El Salvador and Nicaragua, where a combination of oblique convergence, a prominent bend in the trench, and weak or no locking of the subduction interface, University of Wisconsin and University of Arkansas researchers are studying how a volcanic arc and forearc sliver deform in response to oblique convergence. Through Digital Elevation Model analysis, structural field work, GPS observations, and forward and inverse modeling using a three-dimensional, geometrically realistic subduction/forearc finite element mesh, the team is addressing the following important problems: (1) whether changes in convergence obliquity due to bends in trenches are efficiently transferred into changes in forearc motion or deformation and whether escape of a forearc sliver toward the trench (a free surface) is favored over crustal thickening at the leading edge of a forearc sliver; (2) why the bend between the two forearc slivers, where crustal thickening is expected, is instead occupied by a topographic depression (the Gulf of Fonseca); (3) whether the motions of the two forearcs are accommodated by arc-parallel strike-slip faulting, bookshelf faulting, or some combination of the two; (4) whether the east-west stretching characteristic of the crust inboard from the Salvadoran volcanic arc also extends into the forearc and if so, how this stretching interacts with and influences sliver transport. Finally, a series of modeling experiments are being conducted to better understand the kinematics and dynamics of the subduction/forearc wedge system, using a three-dimensional finite element model and a series of plausible boundary conditions, including dip-slip tractions at the base of the wedge, variable resistance to slip along the subduction interface and forearc faults, and varying degrees of buttressing at the leading edge of the wedge. Through this integrated approach to studying active deformation in western Central America with GPS and field-based structural work, the conceptual and kinematic framework for understanding the earthquake cycle in this region is being established. , Tens of thousands of deaths have occurred since 1900 during numerous moderate and large magnitude earthquakes in this region. Knowledge and technology transfer to El Salvadoran and Nicaraguan collaborator significantly benefit future earthquake hazard studies in both countries. Graduate students are being trained in the use of structural geology and high-precision geodesy for studying the earthquake cycle.

在这项为期四年的大地测量和结构研究中，对萨尔瓦多和尼加拉瓜太平洋沿岸的科科斯-加勒比海辐合边缘进行了研究，研究中结合了倾斜辐合、海沟中的突出弯曲以及俯冲界面的弱锁定或无锁定，大学威斯康星州和阿肯色大学的研究人员正在研究火山弧和前弧条如何响应倾斜收敛而变形。通过数字高程模型分析、结构现场工作、GPS 观测以及使用三维、几何真实的俯冲/弧前有限元网格进行正向和逆向建模，该团队正在解决以下重要问题：（1）收敛倾角是否发生变化由于海沟中的弯曲有效地转化为前弧运动或变形的变化，以及前弧条向海沟（自由表面）的逃逸是否比前弧前缘的地壳增厚更有利条子； （2）为什么两个前弧条之间的弯曲处（预计地壳会增厚）却被地形凹陷（丰塞卡湾）占据； (3) 两个前弧的运动是否受到弧平行走滑断层、书架断层或两者的某种组合的调节； (4)萨尔瓦多火山弧内侧地壳的东西向拉伸特征是否也延伸到弧前，如果是的话，这种拉伸如何与银条运输相互作用并影响。最后，正在进行一系列建模实验，以更好地了解俯冲/前弧楔系统的运动学和动力学，使用三维有限元模型和一系列合理的边界条件，包括俯冲滑移牵引力楔形物，沿俯冲界面和弧前断层滑动的可变阻力，以及楔形物前缘不同程度的支撑。通过这种利用 GPS 和现场结构工作研究中美洲西部活动变形的综合方法，正在建立理解该地区地震周期的概念和运动学框架。自1900年以来，该地区发生多次中、大地震，造成数万人死亡。向萨尔瓦多和尼加拉瓜合作者转让知识和技术对两国未来的地震灾害研究大有裨益。研究生正在接受使用构造地质学和高精度大地测量学来研究地震周期的培训。