Collaborative Research: Integrated Studies of Continental Triple Junction Tectonics, Northern Central America

威斯康星大学和加州州立大学斯坦尼斯劳斯分校的一个研究小组与来自萨尔瓦多、危地马拉、洪都拉斯、法国、墨西哥和西班牙的科学家合作，在中美洲北部加勒比海板块变形的西端对断层和地震周期进行了综合研究。主要的重点是更好地测量和模拟危地马拉南部大陆三重结合部周围的形变，在那里，莫塔瓜和波罗契克断层系统终止于加勒比-北美板块边界。来自萨尔瓦多、危地马拉、洪都拉斯和墨西哥南部的110个战役和连续GPS站点的现有和新数据将被汇编和分析，以创建西加勒比地区第一个一致的区域尺度GPS速度场。新的速度场将用于研究四个重要问题，包括：1)大陆三联点周围的变形是如何调节的；2)中美洲弧前银条的运动和内部变形；3)危地马拉的贾尔帕塔瓜断裂和其他火山弧断裂容纳这一运动并与岩浆弧相互作用的方式；4)左行莫塔瓜-波罗契克断裂系统和右行贾尔帕塔瓜断裂之间的伸展如何调节，以及俯冲科科斯板块倾角变化50度对俯冲耦合和上板块变形的影响。将在危地马拉和洪都拉斯收集互补的露头、重力、古地磁、辐射和地球化学数据，为解释和模拟GPS速度场提供地质框架。这项工作将利用正演和反演模型，结合现有的大地测量和构造观测以及适当的地震约束条件，更好地理解决定该地区变形的因素，并优化块体旋转、断层耦合和锁定深度、应变率和准刚性块体内的应变率和方向的估计。这项工作将产生的地震间应变率和长期断层滑移率的估计将为萨尔瓦多、洪都拉斯和危地马拉的风险分析提供信息，这些国家在过去35年里曾发生破坏性地震。这项研究是对邻国(即墨西哥、尼加拉瓜、哥斯达黎加)的公共资助的自然灾害研究的补充，共同将极大地促进中美洲和墨西哥南部大部分地区对这些危害的了解。将在危地马拉和萨尔瓦多举办的培训讲习班将针对一种或多种技术，并将构成一个小型论坛，用于介绍项目成果和教育东道国的学生、科学家和广大公众。

A research team from University of Wisconsin and California State University Stanislaus, in collaboration with scientists from El Salvador, Guatemala, Honduras, France, Mexico, and Spain are carrying out an integrated study of faulting and the earthquake cycle in northern Central America, at the deforming western end of the Caribbean plate. The major emphasis is to better measure and model deformation around a continental triple junction in southern Guatemala, where the Motagua and Polochic fault system terminates the Caribbean-North America plate boundary. Existing and new data from 110 campaign and continuous GPS sites in El Salvador, Guatemala, Honduras, and southern Mexico will be compiled and analyzed to create the first consistent regional-scale GPS velocity field for the western Caribbean. The new velocity field will be used to study four important topics, including: 1) how deformation is accommodated around the continental triple junction; 2) the motion and internal deformation of the Central America forearc sliver; 3) the manner in which the Jalpatagua fault and other volcanic arc faults in Guatemala accommodate this movement and interact with the magmatic arc; and 4) how extension is accommodated between the sinistral Motagua-Polochic fault system and the dextral Jalpatagua fault and the influence on subduction coupling and upper plate deformation of a 50 degree change in the dip of the subducting Cocos plate. Complementary outcrop, gravity, paleomagnetic, radiometric, and geochemical data will be collected in Guatemala and Honduras to provide a geological framework for interpreting and modeling the GPS velocity field. Forward and inverse modeling that integrates the available geodetic and structural observations and suitable earthquake constraints will be used to better understand the factors that dictate deformation in the region and optimize estimates of block rotations, fault coupling and locking depths, and strain rates and directions within quasi-rigid blocks.Estimates of interseismic strain rates and long-term fault slip rates that will result from this work will inform risk analysis in El Salvador, Honduras, and Guatemala, where destructive earthquakes have occurred in the past 35 years. The study complements publicly funded studies of natural hazards in neighboring countries (i.e. Mexico, Nicaragua, Costa Rica) and together will substantially advance understanding of these hazards in much of Central America and southern Mexico. Training workshops to be held in Guatemala and El Salvador will target one or more techniques and will constitute a mini-forum for presenting project results and educating students, scientists, and the broader public in the host countries.