Collaborative Research: Active, Upper Plate Deformation in Response to Migration of the Panama Triple Junction, Pacific Coast, Panama and Costa Rica

这项弧前演化的多学科研究考察了横跨俯冲巴拿马断裂带（一个活跃的转换断层）的俯冲带上部板块的短期（年）和长期（数千年至数百万年）应变模式。该项目的目标是测试几个假设，包括：1)上板块变形主要是与科科斯岭碰撞相关的压痕构造的结果；2) Fila Costena冲断带随着巴拿马三合带的迁移向巴拿马境内横向扩展；3)上板块速度场反映了Cocos Ridge碰撞，包括Fila Costena的缩短，巴拿马断裂带陆上投影的剪切/隆升，以及与地震周期相关的弹性应变。研究小组正在利用结构分析、第四纪地质测绘和年代测定、大地定位系统和建模研究，努力将长期的变形记录与短期的运动学指标结合起来，以便评估上部板块的变形速率和变形风格。Fila Costena冲断带前缘与火山碎屑扇的交点为约束变形提供了极好的时间线。对布里卡半岛海相阶地的放射性碳测年和光学激发发光测年得到了该半岛晚第四纪形变的良好记录。应变分配的大地测量研究将决定短期弹性应变的时空格局。俯冲带是地球上发生最大地震的地方，沿着板块边界的弹性应变不断积累，直到地震期间储存的能量释放出来。通过结合中美洲板块边界上部板块的短期和长期变形指标，可以评估导致地震的弹性或可恢复应变以及平均许多地震影响的永久应变。本项目专门研究了哥斯达黎加南部和巴拿马西南部板块边界的耦合属性，并对这些地区的地震危险性进行了评估。该项目由宾夕法尼亚州立大学和三一大学的主要研究人员指导，涉及研究生和本科生，并与哥斯达黎加和巴拿马的研究人员进行科学合作。该项目由美国国家科学基金会地球科学部构造计划和美国国家科学基金会国际科学与工程办公室支持。

This multidisciplinary study of forearc evolution examines the short term (years) and long term (thousands to millions of years) patterns of strain in the upper plate of a subduction zone that straddles the subducting Panama Fracture Zone, an active transform fault. The project goals are to test several hypotheses, including: 1) upper plate deformation is primarily a consequence of indentation tectonics related to Cocos Ridge collision; 2) the Fila Costena thrust belt is propagating laterally into Panama with the migration of the Panama Triple Junction; 3) the velocity field in the upper plate reflects Cocos Ridge collision, including shortening across the Fila Costena, shear/uplift across the onshore projection of the Panama Fracture Zone, and the elastic strain associated with the earthquake cycle. The research team is using structural analyses, Quaternary geologic mapping and dating, and geodetic GPS and modeling studies in an effort to integrate a long-term record of deformation with short-term indicators of kinematics to allow for assessment of rates and styles of deformation of the upper plate. Intersection of the leading edge of the Fila Costena thrust belt with a volcanic debris fan provides excellent timelines to constrain deformation. Radiocarbon and Optically Stimulated Luminescence dating of a superb flight of marine terraces on the Burica Peninsula yield an excellent record of late Quaternary deformation of the peninsula. Geodetic research of strain partitioning will determine the spatial and temporal patterns of short-term elastic strain.Subduction zones are sites of the largest earthquakes on earth, with buildup of elastic strain along the plate boundary until release of this stored energy during earthquakes. By combining short-term and long-term indicators of deformation in the upper plate of the Middle America plate boundary, the elastic or recoverable strain that leads to earthquakes as well as the permanent strain that averages the effects of many earthquakes can be evaluated. This project specifically addresses the coupling attributes of the plate boundary in southern Costa Rica and southwestern Panama, with an assessment of the earthquake hazard of these regions. The project, under the direction of principal investigators from Pennsylvania State University and Trinity University, involves graduate and undergraduate students and scientific collaborations with Costa Rican and Panamanian researchers. The project is supported by the NSF Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.