Strain Partitioning and Active Faulting During Oblique Convergence, Northern Andes, Ecuador

厄瓜多尔安第斯山脉北部斜辐合过程中的应变划分和活动断层

• 批准号: 0126051
• 负责人: Anne Meltzer
• 金额: $ 3.81万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0126051&HistoricalAwards=false
• 关键词: Strain; Partitioning; Active; Faulting; During

The Andes are the type example of ocean-continent collision. The Nazca plate subducts beneath the South American continent, giving rise to the high mountains along the coast and the great plateaus of the Central Andes. In Ecuador, the imposing Andean arc divides into two volcanic chains that define the eastern and western margins of the Inter Andean Valley, a long, north south oriented topographic low at high elevation. Quito, Ecuador's capital city, sits within the Interandean valley between the two chains. Its 1.5 million citizens live amidst some of the Earth's more active geologic processes and hazards, including active, complex faulting, explosive volcanism, and rapid and extreme erosion and sedimentation driven by the high elevations in the area.The Interandean Valley of Ecuador is an excellent place to study strain partitioning and fault dynamics during oblique convergence. The geology is well mapped and the region is extremely active tectonically making it easy to observe and quantify deformation. A major fault system, the Delores-Guayaquil Megashear, a transpressive dextral strike-slip system, trends onshore at Guayaquil and passes into the Inter Andean Valley. The Delores-Guayaquil Megashear is similar in scale and seismic activity to San Andreas Fault system in California. Like the San Andreas, the Delores-Guayaquil Megashear is a composite fault system, composed of a number of individual fault strands. While portions of the fault system have been identified using offset geomorphic features, sag ponds, and fault scarps, the fault system has not been systematically mapped at the surface. In many places the location of the fault is masked by active erosional and depositional processes. Nowhere has the fault or associated deformation been imaged in the subsurface. There is no coherent framework for integrating the numerous faults and the development of fault-controlled structures into a kinematic model.We are conducting a pilot project to acquire high-resolution seismic reflection profiles in three strategic locations in the Inter Andean Valley to determine subsurface fault/fold geometry and deformation history within the Delores-Guayaquil Megashear. The results of this study will improve our understanding of strain partitioning in transpressional settings and are immediately relevant to assessing the seismic hazards for Quito, Ecuador. This project is a collaborative effort between Lehigh University and the Instituto Geofisico at the National Secular Polytechnic National, Quito, Ecuador.

安第斯山脉是海洋与大陆碰撞的典型例子。纳斯卡板块俯冲到南美大陆之下，形成了沿海的高山和安第斯山脉中部的高原。在厄瓜多尔，雄伟的安第斯弧分为两条火山链，界定了安第斯山谷的东部和西部边缘，这是一条长长的、南北向的高海拔低地地形。厄瓜多尔首都基多位于两条链之间的安第斯山谷内。其 150 万居民生活在地球上一些较为活跃的地质过程和灾害之中，包括活跃、复杂的断层、爆炸性火山活动以及该地区高海拔造成的快速和极端的侵蚀和沉积。厄瓜多尔的安第斯山谷是一个极好的研究倾斜收敛过程中的应变分配和断层动力学的场所。地质图绘制良好，该地区的构造极其活跃，因此很容易观察和量化变形。德洛雷斯-瓜亚基尔大剪切带是一个主要断层系统，它是一种横压性右旋走滑系统，在瓜亚基尔向岸延伸并进入安第斯山谷间。德洛雷斯-瓜亚基尔大剪切带的规模和地震活动与加利福尼亚州的圣安德烈亚斯断层系统相似。与圣安德烈亚斯断层一样，德洛雷斯-瓜亚基尔大剪切带也是一个复合断层系统，由许多单独的断层带组成。虽然已经使用偏移地貌特征、凹陷池和断层陡坡识别了部分断层系统，但尚未在地表系统地绘制断层系统地图。在许多地方，断层的位置被活跃的侵蚀和沉积过程所掩盖。 地下没有任何断层或相关变形被成像。没有一个连贯的框架可以将众多断层和断层控制结构的发展整合到运动学模型中。我们正在开展一个试点项目，以获取安第斯山谷间三个战略位置的高分辨率地震反射剖面，以确定地下断层/德洛雷斯-瓜亚基尔巨型剪切力内的折叠几何结构和变形历史。这项研究的结果将增进我们对压压环境中应变分配的理解，并且与评估厄瓜多尔基多的地震危险直接相关。该项目是理海大学和厄瓜多尔基多国立世俗理工学院 Geofisico 研究所的合作成​​果。