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

将在科罗拉多州和新墨西哥州的里奥格兰德裂谷进行一项宽带和长周期的大地电磁试验，以限制这一大陆内伸展区域之下岩石圈的热状态和流变状态。有关大陆裂谷的重要问题仍未得到解决，包括岩浆作用、挥发分和继承的岩石圈结构在裂谷形成和发展中的作用。最近的地震成像研究表明，在里奥格兰德裂谷之下的上地幔中，地壳变薄，地震波速度很低。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，其区域比裂谷-S的地貌表达-要宽得多。来自试点大地电磁试验的电导率模型将为地震研究提供补充信息，并将与可用于评估热和成分不均质性对裂谷过程的相对贡献的地震模型结合起来。对北部和中部裂谷区段的结果进行比较，将用来评估裂谷的范围和假设的向北传播。大地电磁先导实验将包括两个裂隙横断面，并将对结果进行评估，以评估扩大或修改阵列设计的实验的必要性。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，并将涉及本科生研究人员。

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.