Vp/Vs Structure of the Crust and Reflection Fabric of the Upper Mantle beneath the Southern Appalachians using Teleseismic and Global Phases

使用远震和全球相位研究南阿巴拉契亚山脉下方地壳和上地幔反射结构的 Vp/Vs 结构

• 批准号: 1830182
• 负责人: Robert Hawman
• 金额: $ 11.99万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1830182&HistoricalAwards=false
• 关键词: Vp; Vs; Structure; Crust; Reflection

The purpose of this work is to gain a better understanding of the deep geologic structure of the southeastern U.S., from the Appalachian Mountains to the coast. By using seismic waves generated by distant earthquakes the investigators are able to conduct echo soundings of the Earth's crust and mantle to a depth of 300 km (180 miles). The methodology is adapted in part from exploration techniques used by the petroleum industry. The results from this work, when added to parallel analyses by other researchers, will allow the construction of a three-dimensional model of the subsurface. This model will help us to unravel the sequence of geologic events that led to the formation of the Appalachian mountains and adjacent terrain and the mineral resources found there. The research will provide financial support and valuable technical training for graduate students pursuing careers in the geosciences. The grant will also provide valuable research experience for undergraduate students and will support our ongoing education/outreach program for students in grades 4-6. As of October 2017, the principal investigator had worked with over 2150 elementary and middle-school students (in groups of 15-20 at a time) in outdoor, hands-on exercises in plate tectonics and seismology. The current plan is to expand those activities to additional school districts across the state of Georgia.The passage of USArray across the eastern United States has resulted in fundamentally new insights into the fine-scale structure of the continental lithosphere and has helped to rekindle interest in old mountain belts. The proposed work will use a combination of body waves (Ps, SsPmp, PpPmp. and reflections generated by PKIKP/PKiKP) to enhance our images of the crust and upper mantle across a portion of the southern Appalachians, beneath stations of the SESAME array. The goal of this work is to address the following questions: 1) Can more reliable estimates of average crustal Vp/Vs be obtained across the Atlantic Coastal Plain, where reverberations within very low-velocity sediments tend to overwhelm Ps conversions from the Moho, and what do those values of Vp/Vs tell us about the degree to which the basement in this highly extended region was modified by mafic intrusions during Mesozoic rifting? 2) Are there fundamental differences in small-wavelength reflection fabric that might be used to distinguish lithosphere from asthenosphere? 3) Does strain in the lithosphere occur as distributed shear, or is it typically localized along well-defined shear zones? 4) Can we distinguish between different flow patterns in the mantle - e.g., vertical versus horizontal flow, and if so, can we improve on the vertical resolving power of SKS/PKS/SKKS arrivals to place stronger constraints on depth ranges responsible for observations of shear-wave splitting? Improved estimates of Vp/Vs will be obtained by first constructing localized models of crustal thickness and average crustal P-wave velocity using SsPmp and PpPmp arrivals. The resulting set of localized estimates of crustal thickness and average crustal P-wave velocity will be used to help constrain the grid search for Vp/Vs for stations deployed in the Coastal Plain. For the upper mantle, we will use the global seismic phase PKIKP (PKPdf) as a virtual source to construct normal-incidence reflection sections that are analogous to those produced by active-source reflection profiling of the crust.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.

这项工作的目的是更好地了解从阿巴拉契亚山到海岸的美国东南部的深层地质结构。通过使用远处地震产生的地震波，研究人员能够将地球和地幔的回声发声到300公里（180英里）的深度。 该方法是根据石油行业使用的探索技术进行了调整的。当这项工作的结果添加到其他研究人员的并行分析中时，将允许构建地下的三维模型。 该模型将帮助我们揭示导致阿巴拉契亚山脉和邻近地形以及那里发现的矿产资源形成的地质事件的顺序。 这项研究将为从事地球科学的职业的研究生提供财政支持和宝贵的技术培训。 该赠款还将为本科生提供宝贵的研究经验，并将支持我们为4 - 6年级的学生提供的持续的教育/外展计划。 截至2017年10月，这位首席研究员曾在户外工作，与2150多名中学和中学学生（一次为15-20名），在板块构造和地震学中进行动手练习。 当前的计划是将这些活动扩展到佐治亚州的其他学区。美国阵列遍布美国东部的通道从根本上产生了对大陆岩石圈的精细结构的新见解，并有助于重新激发人们对旧山带的兴趣。 拟议的工作将结合体波（PS，SSPMP，PPPMP。和PKIKP/PKIKP产生的反射）来增强我们在阿巴拉契亚山脉南部的一部分，芝麻阵列的站下的地壳和上层地幔的图像。 这项工作的目的是解决以下问题：1）可以在整个大西洋沿海平原上获得对平均地壳VP/V的更可靠的估计，在该平原中，在非常低速的沉积物中的混响倾向于使Moho的PS转换倒流，从而使这些高度vp/vs vp s Blotified of terified在MA上进行了什么，在MA的基础上是什么，在MA的范围内进行了什么，这是什么样的人数。 2）在小波长反射织物中是否存在基本差异，这些织物可能被用来区分岩石圈和软圈？ 3）岩石圈中的应变是作为分布式剪切而发生的，还是通常沿明确定义的剪切区域进行定位？ 4）我们可以区分地幔中的不同流动模式 - 例如垂直与水平流动，如果是的话，我们是否可以改善SKS/PKS/SKK到达的垂直分辨能力，以对造型的深度范围更加强大的约束，以使剪切波分裂观察？通过首先使用SSPMP和PPPMP到达的局部模型，将获得改进的VP/V估计值。由此产生的一组局部估计值和平均地壳P波速度的局部估计值将用于帮助限制部署在沿海平原上的站点的网格搜索VP/VS。对于上地幔，我们将使用全球地震阶段PKIKP（PKPDF）作为虚拟来源，以构建与地壳主动源反射概况相似的正态分子反射部分，该奖项反映了NSF的法定任务，并通过评估范围来反映了NSF的法定任务，并通过评估范围进行了评估，并经过了范围的范围。

项目成果

P ‐Wave Reflectivity of the Crust and Upper Mantle Beneath the Southern Appalachians and Atlantic Coastal Plain Using Global Phases

P — 使用全球相位的南阿巴拉契亚山脉和大西洋沿岸平原下方的地壳和上地幔的波反射率

• DOI: 10.1029/2020gl089648
• 发表时间: 2020
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Verellen, Devon N.;Alberts, Erik C.;Larramendi, Gustavo A.;Parker, Jr, E. Horry;Hawman, Robert B.
• 通讯作者: Hawman, Robert B.