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

来自威斯康星州大学和加州州立大学的一个研究小组与来自萨尔瓦多萨尔瓦多、危地马拉、洪都拉斯、法国、墨西哥和西班牙的科学家合作，正在加勒比板块变形西端的中美洲北方进行断层和地震周期的综合研究。主要的重点是更好地测量和模拟变形周围的大陆三联点在危地马拉南部，在那里的莫塔瓜和Polochic断层系统终止加勒比-北美板块边界。将对来自萨尔瓦多、危地马拉、洪都拉斯和墨西哥南部110个活动和连续GPS站点的现有和新数据进行汇编和分析，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课题，包括：（1）变形是如何在大陆三联点周围适应的;（2）中美洲弧前狭长体的运动和内部变形;（3）Jalpatagua断层和危地马拉其他火山弧断层适应这种运动并与岩浆弧相互作用的方式;左旋Motagua-Polochic断裂系统与右旋Jalpatagua断裂之间的伸展是如何协调的，以及俯冲科科斯板块倾角改变50 °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补充的露头、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。将利用整合现有大地测量和结构观测以及适当地震约束的正演和反演模型，更好地了解决定该区域变形的因素，并优化对块体旋转、断层耦合和锁定深度的估计，准刚性块体内部的应变率和方向。这项工作得出的长期断层滑动率将为萨尔瓦多、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年中发生了破坏性地震。这项研究补充了由政府资助的对邻国（即墨西哥、尼加拉瓜、哥斯达黎加）自然灾害的研究，并将大大促进对中美洲大部分地区和墨西哥南部自然灾害的了解。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，并将成为介绍项目成果和教育东道国学生、科学家和广大公众的小型论坛。

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.