CAREER: A Comprehensive Seismic Investigation to the Crust and Uppermost Mantle Beneath the South Pole, East Antarctica

非技术性了解南极附近的地下结构将回答南极地球科学中一些最令人兴奋的科学问题，从冰下高山和最南端火山岩的起源到附近冰下湖泊的存在。然而，由于该地区偏远，冰盖较厚，这些问题一直很难回答。使用部署在冰盖顶部的地震台提供了一种通过冰层成像大陆的替代工具，因为地震信号记录了关于下面地壳地质的敏感信息。例如，含有更多放射性元素的地壳岩石可能导致了冰盖融化，形成了冰下湖泊，这些岩石可以通过它们独特的地震特征来识别。该项目计划在南极地区部署新的地震传感器，并收集数据进行一系列现代地震数据分析，以产生各种地震观测数据，以填补知识空白。这些观测数据将被转换成地图，说明下伏地壳的物理性质和化学成分，并进一步帮助确定南极附近下伏地壳的热性质。这些观察将提供对冰下地质的第一级评估，并深入了解冰下地貌的起源，如横贯北极的山脉和许多冰下湖泊。该项目将与长岛的K-12学区和社区大学合作，提供免费的地球科学辅导、公开讲座，并邀请K-12教育工作者教授现场学生。这些努力将突出极地地球科学在气候变化中的重要性，并提高对地球科学作为高中生可行职业道路的认识。从技术上讲，南极300公里范围内的区域及其冰下结构对研究南极地球科学同样至关重要，甚至更重要。鉴于其位于南极洲南部高地和东南极克拉通之间的门户位置，该地区对于研究大陆的地质历史和现代构造、模拟大陆动力学以及开发更准确的冰盖动力学模型以预测其对全球气候变化的反应至关重要。然而，由于非洲大陆的偏远和厚厚的冰盖，这些特性还没有得到系统的研究。在这项拟议的研究中，该小组将在南极附近部署约180个高频3分量便携式地震节点和8个宽带传感器，包括附近的南极洲横贯北极山脉和极地冰下盆地。线性节点阵列和二维宽带阵列的组合将提供空间复盖和解决高分辨率地下结构变化的能力。一旦收集到数据，该团队将应用一套为阵列和研究区域量身定做的数据处理方案，包括1)确定地壳和最上地幔的各向同性和各向异性结构的综合面波分析；2)测量亚冰层和泊松比的两层接收函数分析；3)建立具有不确定性的地震模型的联合面波和接收函数反演；4)一种新的地壳成分分析，它利用地震属性来量化地壳中的二氧化硅含量；5)一种联合蒙特卡罗热反演，它将居里深度测量与地震约束的地壳热产生相结合，以构造自洽、均匀的地壳地温。这项研究得到了一个全面的教育部分的补充，该部分为研究生以及长岛高需求的K-12学区和社区大学提供高质量的地球科学教育。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NontechnicalUnderstanding the subsurface structure near the South Pole will answer some of the most exciting scientific questions in Antarctic Earth Science, ranging from the origin of the high subglacial mountains and the southernmost volcanic rocks to the existence of nearby subglacial lakes. However, it has been difficult to answer these questions since the area is remote and the ice cover is thick. Using seismic stations deployed on top of the ice sheet provides an alternative tool to image the continent through the ice, as seismic signals record sensitive information about the geology of the crust below. For example, crustal rocks with more radioactive elements may have caused the ice sheet to melt, creating subglacial lakes, and these rocks can be identified by their unique seismic signatures. This project plans to fill a knowledge gap by deploying new seismic sensors in the South Pole area and collecting data to perform a suite of modern seismic data analyses to produce a variety of seismic observables. These observables will be translated into maps illustrating the physical properties and chemical composition of the underlying crust, and further help determine the thermal properties of the underlying crust near the South Pole. These observations will provide a first-order assessment of the sub-ice geology and insights into the origins of the features such as the Transantarctic Mountains and numerous subglacial lakes. The project will collaborate with K-12 school districts and community colleges in Long Island and provide free geoscience tutoring, public lectures, and inviting K-12 educators to teach students from the field. These efforts will highlight the importance of polar geosciences in a changing climate and elevate the awareness of earth science as a viable career path for high school students. Technical The area within 300 km of the South Pole and its sub-ice structures are equally, if not more, critical in studying Antarctic earth sciences. Given its gateway locality between the high southern Transantarctic Mountains and East Antarctic craton, the area is critical for studying geological history and modern tectonism of the continent, modeling continental dynamics, and developing more accurate ice sheet dynamic models to predict their response to the global climate change. However, these properties have not been systematically studied due to both the remoteness of the continent and its thick ice coverage. In this proposed study, the team will deploy ~ 180 high-frequency 3-component portable seismic nodes and eight broadband sensors near the South Pole, encompassing the nearby southern Transantarctic Mountains and the polar subglacial basins. A combination of linear nodal arrays and 2-dimensional broadband arrays will provide both spatial coverage and the capability to resolve high-resolution subsurface structural variations. Once the data are collected the team will apply a suite of data processing schemes tailored for the array and study area, including 1) a comprehensive surface wave analysis that determines both the isotropic and anisotropic structure of its crust and uppermost mantle; 2) 2-layer receiver function analysis that measures sub-ice layering and Poisson’s ratio; 3) a joint surface wave and receive function inversion that builds seismic models with uncertainties; 4) a novel crustal compositional analysis which uses the seismic attributes to quantify the silica content of the crust, and 5) a joint Monte Carlo thermal inversion that combines Curie-depth measurements with seismologically constrained crustal heat generation to construct a self-consistent, uniform crustal geotherms. This research is complemented by a comprehensive educational component that provides high-quality earth science education to graduate students, as well as to high-need K-12 school districts and community colleges in Long Island.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.