A GPS Study of the Large-Scale Neotectonics of Northern Central America

该项目是一项为期五年的中美洲北部大规模新构造合作大地测量学研究，加勒比板块西端与中美洲俯冲带和莫塔瓜-波洛奇走滑断层系统相邻。科学目标如下：(1)估计沿Cocos-Caribbean俯冲界面的摩擦耦合的大小和分布；(2)测量横跨motaagua - polochic断裂系统的一个或多个点的走滑运动速率；(3)测量横跨motaagua - polochic断裂系统南部的中美洲“盆地和山脉”的延伸；(4)测量应变在中美洲火山弧断层上积累的速度有多快，这些断层适应了斜向俯冲引起的右弧前切变；(5)测试是否发生了显著的区域隆起，可能是由于该地区俯冲下的板块的假设剥离；(6)改进加勒比板块大地测量参考框架的运动学模型。关于第一个目标的工作有助于对地震过程在适应俯冲方面的基本作用的新认识。目标2-5的进展正在推进目前对加勒比板块西部后缘新构造和地震危险的贫乏理解。在最终目标上的工作有利于美国国家科学基金会赞助的多个GPS研究，这些研究围绕着加勒比海板块复杂变形的边缘。这些目标正在通过对分布在洪都拉斯、危地马拉和萨尔瓦多的50-100个GPS站点的年度或更频繁的占领所确定的速度和已经在这些国家运行的7个连续GPS站点的速度进行建模来实现。建模使用三维有限元代码，允许研究区域的构造真实表示，包括代表海洋-大陆俯冲边界的横向和垂直变化的材料属性。所有的测量都是由当地科学家完成的，除了最初的网络侦察和安装，这是一个合作的努力。该项目旨在显著促进与之合作的洪都拉斯、危地马拉和萨尔瓦多科学家的研究事业。预算包括年度运营资金、GPS接收器、洪都拉斯地震学家和危地马拉地震学家的旅行资金，可能还包括一名来自萨尔瓦多的地球科学家。最终，上述目标的进展将改善对这一广阔地区存在地震危险的各种断层沿线重大地震可能发生频率的估计。

This project is a five-year collaborative geodetic study of the large-scale neotectonics of northern Central America, where the western end of the Caribbean plate abuts both the Middle America subduction zone and Motagua-Polochic strike-slip fault system. The scientific objectives are as follows: (1) Estimate the magnitude and distribution of frictional coupling along the Cocos-Caribbean subduction interface, (2) Measure the rate of strike-slip motion at one or more points across the Motagua-Polochic fault system, (3) Measure extension across the Central American "basin-and-range" south of the Motagua-Polochic fault system, (4) Measure how quickly strain accumulates across faults in the Central American volcanic arc that accommodate dextral forearc shear in response to oblique subduction, (5) Test whether significant regional uplift occurs, possibly in response to the hypothesized detachment of the slab subducting beneath this region, and (6) Improve kinematic models of the Caribbean plate geodetic reference frame. Work on the first objective is contributing to an emerging understanding of the fundamental role of aseismic processes in accommodating subduction. Progress on objectives 2-5 is advancing the present poor understanding of the neotectonics and seismic hazards at the western, trailing edge of the Caribbean plate. Work on the final objective benefits multiple NSF-sponsored GPS studies of deformation around the complexly deforming margins of the Caribbean plate. These objectives are being accomplished through modeling of velocities determined from annual or more frequent occupations of 50-100 GPS sites distributed throughout Honduras, Guatemala, and El Salvador and velocities at seven continuous GPS sites that are already operating in these countries. Modeling is done using three-dimensional finite element code that allows for a tectonically realistic representation of the study area, including laterally- and vertically-varying material properties representative of an ocean-continent subduction boundary. All measurements are made by local scientists, except for the initial network reconnaissance and installation, which were a collaborative effort.The project is structured to benefit significantly the research careers of Honduran, Guatemalan, and Salvadoran scientists with whom are collaborating. The budget includes annual operating funds, GPS receivers, and travel funds for Honduran seismologist and Guatemalan seismologists, and possibly an earth scientist from El Salvador. Ultimately, progress on the goals above will improve estimates of the likely frequency of significant earthquakes along a variety of faults that present a seismic hazard in this extensive region.