Collaborative Research: Northern Embayment Lithosphere Experiment (NELE)

地球望远镜可移动阵列横跨密西西比湾的通过为研究与活动变形和古老的克拉通内裂谷有关的岩石圈结构提供了机会。密西西比湾是北美大陆的一级地质构造，具有悠久而复杂的地质历史，至少受两次大陆裂解的影响。最近盆地下沉的地质原因是个谜，因为大约1亿年前开始下沉，而且与重大构造事件无关。此外，活动的新马德里地震带(NMSZ)位于密西西比湾北部的上地壳。岩石圈地震速度的不均一性和各向异性可能是该地区与盆地下沉和地震成因有关的动力学过程的指示器。地震实验结合了EarthScope的可移动台站和更高密度的FlexArray布设，以提供超过上地幔过渡带深度的岩石圈速度和各向异性结构的总体框架。与海湾轴线垂直和平行的深层结构的详细变化是使用在密西西比湾内外延伸的三条密集的FlexArray站线进行成像的。讨论的主要问题包括1)海湾与周围地区岩石圈结构的主要差异，2)早寒武世裂谷的性质及其与原有构造的关系，3)盆地下沉的动力学过程，以及4)NMSZ与大尺度岩石圈结构的关系。这是通过联合解释地震速度层析成像、势场、传递/接收函数以及使用传统和新地球物理技术生成的随深度变化的各向异性图像来实现的。

Passage of the EarthScope Transportable Array across the Mississippi Embayment is providing an opportunity to investigate lithospheric structure associated with active deformation and an ancient, intracratonic rift. The Mississippi Embayment is a first-order geological structure of the North American continent with a long and complex geological history affected by at least two periods of continental breakup. The reason for geologically recent basin subsidence is enigmatic since subsidence began about 100 million years ago and is not linked to a major tectonic episode. In addition, the active New Madrid seismic zone (NMSZ) is located in the upper crust within the northern Mississippi Embayment. Lithospheric seismic velocity heterogeneity and anisotropy are likely indicators of the dynamic processes associated with basin subsidence and earthquake genesis in the region.The seismic experiment incorporates stations of EarthScope's Transportable Array and a higher density FlexArray deployment to provide an overall framework of lithospheric velocity and anisotropy structure to depths exceeding the upper mantle transition zone. Detailed variations in deep structure perpendicular and parallel to the embayment axis are imaged using three dense lines of FlexArray stations that extend within and outside of the Mississippi Embayment. Major issues that are addressed include 1) the primary differences in lithospheric structure between the embayment and the surrounding region, 2) the nature of early Cambrian rifting and relationship to pre-existing structure, 3) the dynamic processes responsible for basin subsidence, and 4) the relationship of the NMSZ to large scale lithospheric structure. This is accomplished through joint interpretation of seismic velocity tomography, potential fields, transfer/receiver functions, and depth-dependent anisotropy images generated using traditional and new geophysical techniques.