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

格兰德裂谷是北美构造活跃的西部边缘最东端的变形省。位于科罗拉多高原以东的裂谷正在经历伸展和伸展，地震发生的可能性略高于周围地区。运动速度估计为亚毫米到5毫米/年，但总伸展测量的不确定度通常与估计值本身相同。该项目汇集了科罗拉多大学博尔德大学和新墨西哥大学的一组研究人员，以高精度确定格兰德河裂谷的当前运动速度。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)仪器测量裂缝的运动。每个测量时期持续六个月，正在收集四个时期的数据，提供涵盖三年跨度的费率。该地区的缓慢运动速度使这一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以最佳方式解决每年亚毫米级的变形。该项目的一个主要目标是了解在表面测量的拉伸速率对于板块在更深层次的拉伸意味着什么。一种耐人寻味的可能性是，格兰德河裂谷的伸展是不同的，地壳和地幔的作用过程不同。现有的地质观察还表明，裂谷的性质从北到南发生了巨大的变化，科罗拉多州和新墨西哥州北部以线性地形凹陷为标志的狭窄裂谷区逐渐延伸到新墨西哥州中南部的多个山谷(“盆地和山脉”)的广阔区域。推动格兰德河裂谷这种多变特征的因素尚未被很好地理解，但可能对我们理解构造板块如何以及为什么经历伸展以及裂谷带内的地震和火山灾害具有重大影响。为了检验这些问题，研究小组正在将他们测量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。这些不同的数据集正被用来建立控制构造板块如何经历裂谷的过程的计算机模型。该项目涉及培训研究生和本科生进行GPS测量和分析，并通过各种方式传播该组织的知识，其中包括：培训K-12学校教师在研究过程中(CU Boulder环境科学合作研究的“地球工程”项目)；让中学参与GPS站点的选址和“采用”；以及与对格兰德裂谷沿线的地震和火山灾害感兴趣的机构进行互动，包括国家地质调查局、地方和联邦应急管理机构、地方政府、城市规划者和工程师。

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.