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

该项目是对中美洲北方大规模新构造进行的一项为期五年的大地测量合作研究，加勒比板块西端毗邻中美洲俯冲带和莫塔瓜-波罗奇克走滑断层系统。 科学目标如下：（1）估计沿可可-加勒比俯冲界面沿着的摩擦耦合的大小和分布，（2）测量横跨莫塔瓜-波罗奇克断层系统的一个或多个点的走滑运动速率，（3）测量横跨莫塔瓜-波罗奇克断层系统以南的中美洲“盆岭”的延伸，（4）测量应变在中美洲火山弧中跨越断层积累的速度，这些断层适应右向弧前剪切以响应斜向俯冲，（5）测试是否发生显著的区域隆起，可能是响应假设的在该区域下方俯冲的板片的剥离，（6）改进加勒比板块大地参照框架的运动学模型。 关于第一个目标的工作正在促进对海侵过程在容纳俯冲作用方面的基本作用的理解。 在目标2-5方面取得的进展正在改善目前对加勒比板块西部后缘的新构造运动和地震危险的认识。 关于最终目标的工作有利于多个NSF赞助的加勒比板块复杂变形边缘周围变形的GPS研究。 这些目标是通过对分布在洪都拉斯、危地马拉和萨尔瓦多各地的50-100个全球定位系统站点每年或更频繁的占用所确定的速度以及这些国家已经在运行的七个连续的全球定位系统站点的速度进行建模来实现的。 建模是使用三维有限元代码，允许一个构造现实的代表性的研究领域，包括横向和垂直变化的材料特性代表的大洋大陆俯冲边界。 除了最初的网络侦察和安装是合作努力之外，所有测量都是由当地科学家进行的。该项目的结构是为了使与之合作的哥伦比亚、危地马拉和萨尔瓦多科学家的研究事业受益匪浅。 预算包括每年的运作资金、全球定位系统接收器、厄瓜多尔地震学家和危地马拉地震学家的旅费，可能还有一名来自萨尔瓦多的地球科学家。 最终，在上述目标上取得的进展将改善对沿着各种断层发生重大地震的可能频率的估计，这些断层在这一广阔地区构成地震危险。

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.