NSF EAGER: Pilot Study: Deep Electrical Structure of the Rio Grande Rift to Constrain Extent and Mechanisms of Rifting

将在科罗拉多和新墨西哥州的格兰德河裂谷上进行一项宽频带和长周期大地电磁试验，以便对这一大陆内伸展区域之下岩石圈的热状态和流变状态提供限制。关于大陆裂谷作用的重要问题仍然没有解决，包括岩浆作用、挥发分和继承的岩石圈结构在裂谷作用的开始和发展中的作用。最近的地震成像研究显示，格兰德河裂谷下的上地幔地壳变薄，地震波速度较低。新的大地测量工作证实了该地区的低应变率环境，并显示出令人惊讶的广泛和均匀的变形面积远远超过裂谷？的地文表达。大地电磁试验的电导率模型将为地震研究提供补充信息，并将与地震模型相结合，可用于评估热和成分不均匀性对裂谷过程的相对贡献。将利用对北方和中央裂谷段的结果进行比较来评估裂谷的范围和假定的向北扩展。大地电磁学试点实验将包括两个裂缝断面，将对实验结果进行评价，以评估是否需要扩大或修改阵列设计。除了更好地了解低应变率环境的社会重要性外，该项目还将支持一名博士生，并将涉及本科研究人员。

A wideband and long period magnetotelluric pilot experiment will be conducted across the Rio Grande Rift in Colorado and New Mexico in order to provide constraints on the thermal and rheological state of the lithosphere beneath this region of intra-continental extension. Important questions about continental rifting remain unresolved, including the role of magmatism, volatiles, and inherited lithospheric structure in the initiation and development of rifting. Recent seismic imaging studies show thinned crust and low seismic wavespeeds in the upper mantle beneath the Rio Grande Rift. New geodetic work confirms the low strain-rate environment of the region, and shows surprisingly broad and uniform deformation over an area far wider than the rift?s physiographic expression. Electrical conductivity models from the pilot magnetotelluric experiment will provide information complementary to seismic studies, and will be combined with seismic models can be used to assess the relative contribution of thermal and compositional heterogeneity to the rifting process. A comparison of results from northern and central rift segments will be used to assess extent and hypothesized northward propagation of the rift. The magnetotellurics pilot experiment will include two rift transects, and the results will be evaluated to assess the need for an experiment with expanded or modified array design. In addition to the societal importance of better understanding low strain-rate environments, this project will support a PhD student and will involve undergraduate researchers.