Collaborative Research: Crustal Deformation Measurements and a Multidisciplinary Geophysical Investigation of the Rio Grande Rift

[04:43 . 37]里约热内卢大裂谷是构造活跃的北美西部边缘最东端的变形省。位于科罗拉多高原东部，裂谷正在经历拉伸和延伸，地震发生的可能性略高于周围地区。运动速率估计为亚毫米至5毫米/年，但测量总延伸的不确定性通常与估计本身的不确定性相同。这个项目汇集了来自科罗拉多大学博尔德分校和新墨西哥大学的一组研究人员，以高精度地确定目前沿里约热内卢格兰德裂谷的运动速率。该团队正在科罗拉多州和新墨西哥州的24个地点使用最先进的全球定位系统（GPS）仪器测量裂缝运动。每个测量历元持续六个月，收集的数据为四个历元，提供的速率包括三年的跨度。该地区缓慢的移动速度使这个项目特别具有挑战性。纪念碑、观测时间和创新的后处理策略旨在最佳地解决亚毫米/年尺度的变形。该项目的一个主要目标是了解在表面测量的拉伸速率意味着板块在更深层次的拉伸。一种有趣的可能性是，b里约热内卢大裂谷的拉伸是不均匀的，地壳和地幔的拉伸过程不同。现有的地质观测还表明，裂谷的特征从北向南变化很大，在科罗拉多州和新墨西哥州北部，一个以线性地形洼地为标志的狭窄裂谷带，在新墨西哥州中南部，一个由多个山谷（“盆地和山脉”）组成的广阔地区。驱动里约热内卢大裂谷这种可变特征的因素尚不清楚，但可能对我们理解构造板块如何以及为什么经历拉伸以及裂谷带内的地震和火山灾害具有重要意义。为了研究这些问题，研究小组正在将他们测量到的运动速度与所有其他可用的数据集进行比较，包括地壳和地幔的地震速度、重力、地表热流和地质数据。这些不同的数据集被用来建立控制构造板块如何经历裂谷过程的计算机模型。该项目涉及对研究生和本科生进行GPS测量和分析方面的培训，并以各种方式传播小组的知识，包括：在研究过程中培训K-12学校教师（科罗拉多大学博尔德分校环境科学合作研究的“土方工程”项目）；让中学参与GPS站点的选址和“采用”；以及与州地质调查局、地方和联邦应急管理机构、地方政府、城市规划者和工程师等对大裂谷沿线地震和火山灾害感兴趣的机构的互动。

0454372RoyThe Rio Grande rift is the easternmost deforming province within the tectonically active western margin of North America. Located just east of the Colorado Plateau, the rift is undergoing stretching and extension manifested by slightly higher probabilities of earthquake occurrence than in surrounding regions. Rates of motion are estimated at sub-mm to 5 mm/yr, but uncertainties in measurements of total extension are typically of the same order as the estimates themselves. This project brings together a team of researchers from the University of Colorado Boulder and the University of New Mexico to establish current rates of motion along the Rio Grande rift with high precision. The team is measuring rift motions using state-of-the-art global positioning system (GPS) instruments at 24 sites in Colorado and New Mexico. Each measurement epoch lasts six months and data are being collected for four epochs, providing rates encompassing a three-year span. The slow rates of motion in the region make this project especially challenging. The monumentation, observing time, and innovative post-processing strategies are designed to optimally resolve deformation at the sub-millimeter per year scale. A primary goal of the project is to understand what stretching rates measured at the surface imply about the stretching of the plate at deeper levels. An intriguing possibility is that stretching in the Rio Grande rift is heterogeneous, with different processes operating in the crust and the mantle. Available geologic observations also suggest that the character of the rifting changes dramatically from north to south, with a narrow rift zone marked by linear topographic depressions in Colorado and northern New Mexico grading to a broad region of multiple valleys ("basin and range") in south-central New Mexico. The factors that drive this variable character of the Rio Grande rift are not well-understood, but could have significant bearing on our understanding of how and why tectonic plates undergo stretching and of earthquake and volcanic hazards within rift zones. To examine these issues, the team is comparing their measured rates of motion with all other available datasets, including seismic velocities in the crust and mantle, gravity, surface heat flow, and geologic data. These diverse datasets are being used to build computer models of processes that control how tectonic plates undergo rifting. The project involves training graduate and undergraduate students in GPS measurement and analysis and spreading the group's knowledge in a variety of ways, including: training K-12 school teachers in the research process (the 'Earthworks' project of the Cooperative Research in Environmental Sciences at CU Boulder); involving middle schools in the siting and "adoption" of GPS sites; and interactions with agencies interested in earthquake and volcanic hazards along the Rio Grande rift including state Geological surveys, local and federal emergency management agencies, local governments, city planners, and engineers.