Collaborative Research: Northern Embayment Lithosphere Experiment (NELE)

EarthScope可移动阵列穿越密西西比湾的通道为研究与活动变形和古老的克拉通内裂谷相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，具有漫长而复杂的地质历史，至少经历了两次大陆裂解。 从地质学上讲，最近盆地沉降的原因是神秘的，因为沉降开始于大约1亿年前，并且与主要的构造事件无关。 此外，活跃的新马德里地震带（NMSZ）位于北方密西西比湾内的地壳上部。 岩石圈地震速度的不均匀性和各向异性可能是与盆地沉降和地震成因相关的动态过程的指标在region.The地震实验结合EarthScope的移动式阵列和更高密度的FlexArray部署站，以提供岩石圈速度和各向异性结构的整体框架，深度超过上地幔过渡带。 使用在密西西比海湾内外延伸的三条密集的FlexArray站线，对垂直和平行于海湾轴线的深层结构的详细变化进行成像。 讨论的主要问题包括：1）海湾与周边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先存构造的关系，3）盆地沉降的动力学过程，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，传输/接收器功能，并使用传统的和新的地球物理技术产生的深度相关的各向异性图像。

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.