Collaborative Research: Northern Embayment Lithosphere Experiment (NELE)

合作研究：北湾岩石圈实验（NELE）

• 批准号: 1053530
• 负责人: Charles Langston
• 金额: $ 62.43万
• 依托单位: University of Memphis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1053530&HistoricalAwards=false
• 关键词: Collaborative; Research; Northern; Embayment; Lithosphere

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.

地球范围可移动阵列穿越密西西比海湾，为研究与活跃变形和古克拉通内裂谷有关的岩石圈结构提供了机会。密西西比海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，受到至少两个大陆分裂时期的影响。地质上最近盆地下沉的原因是一个谜，因为下沉开始于大约1亿年前，与一个主要的构造事件无关。此外，活跃的新马德里地震带（NMSZ）位于密西西比海湾北部的上地壳。岩石圈地震速度的非均质性和各向异性可能是该地区与盆地沉降和地震发生有关的动力过程的指标。地震实验结合了EarthScope的可移动阵列和高密度FlexArray部署，提供了岩石圈速度和各向异性结构的总体框架，深度超过上地幔过渡带。垂直和平行于海湾轴线的深层结构的详细变化使用FlexArray站的三条密集线进行成像，这些线延伸到密西西比海湾内外。研究的主要问题包括：1)河口与周边岩石圈结构的主要差异；2)早寒武世裂陷的性质及其与原有构造的关系；3)盆地沉降的动力过程；4)NMSZ与大范围岩石圈结构的关系。这是通过联合解释地震速度层析成像、位场、传递/接收函数以及使用传统和新的地球物理技术生成的与深度相关的各向异性图像来完成的。