CAREER: Illuminating the Tectonic History of North America with Seismic Models of Shear Attenuation and Velocity

职业：用剪切衰减和速度的地震模型阐明北美的构造历史

• 批准号: 1553367
• 负责人: Colleen Dalton
• 金额: $ 52.14万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2023-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1553367&HistoricalAwards=false
• 关键词: CAREER; Illuminating; Tectonic; History; North

Title: CAREER: Illuminating the Tectonic History of North America with Seismic Models of Shear Attenuation and VelocityThe North American continent contains vastly diverse geology, from the volcanoes and mountains in the west to the interior plains that anchor the central United States and the broad Appalachian hills that roll into the Atlantic Ocean. This topography reflects the many episodes of continental collision, breakup, and modification that the land mass has experienced over billions of years. The movements of the tectonic plates at Earth?s surface are inextricably linked to the movement of rocks in Earth?s mantle (mantle convection). Understanding the connection between the Earth?s interior and surface is essential to addressing fundamental questions about how continents are created, how they evolve over time, and how they are destroyed. This study will use seismic waves generated by earthquakes to image the properties of the crust and mantle beneath North America, with particular emphasis on imaging in three dimensions the energy loss (attenuation) experienced by seismic waves. While it is generally acknowledged that seismic attenuation has the potential to be a valuable source of information about the Earth?s interior, it is difficult to isolate attenuation from other wave-propagation phenomena, which has historically limited its use by researchers. Integrated research and education activities will utilize data recorded by the NSF EarthScope USArray seismometers, which have recorded what is likely the best data set in existence to confront these challenges.This project will investigate, using new data analysis and seismic-wavefield simulations, the three-dimensional variations in shear attenuation beneath North America. This study will also develop a 3-D model of shear velocity in the upper mantle and, through joint interpretation with the attenuation model and laboratory measurements of attenuation and wave speed, place constraints on the variations in temperature, composition, partial melt, and water in the North American upper mantle. The attenuation model will be derived from measurements of Rayleigh wave amplitude and body-wave attenuation at USArray stations throughout the contiguous United States, and the velocity model will be derived from Rayleigh wave travel-time and local site-amplification observations. Separating the competing effects of focusing by elastic structure and anelastic decay on the Rayleigh wave amplitudes is the primary obstacle to imaging small-scale attenuation variations; spectral-element simulations with high-resolution elastic models for the U.S. that have been made possible by USArray will be used to compute focusing effects with greatly improved accuracy. The educational activities are targeted at high-school and undergraduate students. Educational seismometers will be installed at two Providence, RI area high schools. Data recorded by these seismometers and USArray stations will be used to engage the high-school students in earthquake science, fundamental properties of waves, and the tectonic history of North America. Teaching modules utilizing these data that address the Next Generation Science Standards (NGSS) will be developed and disseminated more widely. At the undergraduate level summer interns will carry out research projects at Brown during three summers, and a new field course in Environmental Geophysics will be developed.

标题：职业：通过剪切衰减和速度的地震模型来阐明北美的构造历史，北美大陆构成了众多的地质学，从西部的火山和山脉到锚定美国中部和宽阔的阿巴拉契亚山丘的内部平原。该地形反映了土地质量经历了数十亿年的大陆碰撞，分手和修改的许多事件。地球表面的构造板的运动与地球岩石（地幔对流）的岩石运动密不可分。了解地球之间的内部和表面之间的联系对于解决有关如何创造大陆，它们如何随着时间的流逝以及如何被破坏的基本问题至关重要。这项研究将使用地震产生的地震波来对北美下面的地壳和地幔的特性进行图像，并特别强调在三个维度上成像，地震波经历的能量损失（衰减）。尽管人们普遍认为地震衰减有可能成为有关地球内部的宝贵信息来源，但很难将衰减与其他波浪传播现象隔离开来，这在历史上一直限制了研究人员的使用。综合研究和教育活动将利用NSF Earthscope USArray地震仪记录的数据，这些数据记录了面对这些挑战的最佳数据，该项目将使用新的数据分析和北部北部削皮衰减中的三维变化进行调查。这项研究还将开发上地幔中的3D剪切速度模型，并通过与衰减和波速的衰减模型和实验室测量的联合解释，对北美上层地幔的温度，成分，部分熔体和水的变化构成限制。衰减模型将来自整个连续美国的USARRAY站的瑞利波幅度和人体波衰减的测量，速度模型将源自雷利波波旅行时间和局部位点放大观测值。通过弹性结构和无弹性对雷利波幅度的竞争效果分开是成像小规模衰减变化的主要障碍。 USARRAY使美国已成为可能的高分辨率弹性模型的光谱元素模拟将以极大的提高来计算聚焦效果。教育活动针对高中和本科生。教育地震仪将安装在RI地区高中的两个普罗维登斯。这些地震仪和USARRAY站记录的数据将用于吸引高中生参与地震科学，海浪的基本特性以及北美的构造历史。利用这些数据来解决下一代科学标准（NGSS）的教学模块将得到更广泛的开发和传播。在三个夏天，暑期实习生将在本科生，暑期实习生将在布朗开展研究项目，并将开发一个新的环境地球物理学实地课程。