Ambient Noise and Teleseismic Tomography to infer the Physical State and Structure of the Crust and Upper Mantle in the Western United States

环境噪声和远震断层扫描推断美国西部地壳和上地幔的物理状态和结构

• 批准号: 0711526
• 负责人: Michael Ritzwoller
• 金额: $ 27.66万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711526&HistoricalAwards=false
• 关键词: Ambient; Noise; Teleseismic; Tomography; infer

We seek to advance and apply two powerful new complementary methods of surface wave tomography to rapidly accruing data resources in the western US, predominantly from the Transportable Array (TA) component of EarthScope/USArray. The two methods are ambient noise tomography and two-plane wave teleseismic tomography. Ambient noise tomography (ANT) is based on the extraction of surface-wave Green functions by cross-correlating long sequences of ambient or background seismic noise that form part of the random seismic wavefield. Two plane-wave tomography (TPWT) interprets the variation in amplitude and phase of teleseismic surface waves observed across a regional seismic array in terms of phase velocity variations within the foot-print of the array and, importantly, also models corrugations in the incoming wavefield caused by scattering that occurs between the earthquake and array.Both methods measure surface wave dispersion, but in complementary period bands: ANT (6 - 40 sec) and TPWT (25 - 150 sec). Used in combination, the methods are able to produce dispersion curves (Rayleigh and Love wave, group and phase velocity) across the entire TA from about 6 sec to 150 sec period on a 25-50 km geographic grid. This prospect could not have been foreseen by surface wave seismologists as little as 3 years ago. The information content contained in these dispersion curves at the resolution of these methods ($\sim$70 km across the TA) over a region as large as that proposed is unprecedented. The proposed research will interpret the dispersion maps in terms of shear velocity variations within the crust and upper mantle to a depth of 200 km using a Monte-Carlo method, which returns both the 3-D model and uncertainties. The research proposed here will have a profound impact on the understanding of the physical state and structure of the crust and upper mantle beneath the western US.We anticipate significant impacts on studies of regional-scale tectonics as well as the thermal and compositional state of the lithosphere beneath the western US and, by extension, similar continental regions elsewhere in the world. The proposed data processing and integrative inversion methodology will offer a unique educational experience for the students and post-doctoral staff involved. Moreover, the methods applied to the USArray data are applicable elsewhere as other regional arrays are installed; e.g., in Europe and China and also for PASSCAL installations. The research team has a strong track record of making data products, models, and software available to a wide community, and the data sets, dispersion maps, and models that result from this research will be made generally available. The resulting model also will have relevance for seismic hazard assessment, both for ground motion simulation and to improve and extend community models such as the SCEC 3D reference model. Finally, the application of the new high-resolution inversion methods will help to achieve the vision of the USArray?modeling the Earth beneath the US in unprecedented detail. Movies produced by the research team that track the emergence of dispersion maps as the Transportable Array has been deployed are shown regularly at EarthScope review meetings. The results of the proposed research will also be seen as important components in achieving the US seismological community''s vision for EarthScope.

我们寻求推进和应用两个强大的新的互补方法的面波层析成像，以迅速积累的数据资源，主要是从可移动阵列（TA）的EarthScope/USAray组件在美国西部。这两种方法是背景噪声层析成像和双平面波回波层析成像。 环境噪声层析成像（ANT）是基于通过互相关形成随机地震波场的一部分的环境或背景地震噪声的长序列来提取表面波绿色函数。双平面波层析成像（TPWT）根据阵列足迹内的相速度变化，解释了在区域地震台阵上观测到的地震面波的振幅和相位变化，重要的是，还对地震和台阵之间发生的散射引起的入射波场的波纹进行了建模。两种方法都测量面波频散，但在互补的周期带中：ANT（6 - 40秒）和TPWT（25 - 150秒）。 结合使用，这些方法能够在25-50 km的地理网格上从约6秒到150秒的时间段内产生整个TA的频散曲线（瑞利波和Love波，群速度和相速度）。 这一前景在3年前是面波地震学家所不能预见的。 在这些方法的分辨率（跨越TA的70公里）的这些色散曲线中包含的信息内容在一个区域一样大，建议是前所未有的。拟议的研究将使用蒙特-卡罗方法，根据地壳和上地幔内至200公里深处的剪切速度变化解释色散图，该方法既可返回三维模型，又可返回不确定性。 这里提出的研究将产生深远的影响，对理解的物理状态和结构的地壳和上地幔下的美国西部。我们预计显着的影响，区域尺度的构造研究，以及岩石圈的热和成分状态下的美国西部，并通过扩展，类似的大陆地区在世界其他地方。拟议的数据处理和综合反演方法将提供一个独特的教育经验，为学生和博士后工作人员参与。此外，应用于USAray数据的方法也适用于安装其他区域阵列的其他地方;例如，在欧洲和中国，也适用于PASSCAL装置。该研究团队在向广泛的社区提供数据产品、模型和软件方面有着良好的记录，从这项研究中产生的数据集、分散图和模型将普遍提供。由此产生的模型也将有相关的地震危险性评估，无论是地面运动模拟，并改善和扩展社区模型，如SCEC三维参考模型。最后，新的高分辨率反演方法的应用将有助于实现USAray的愿景？以前所未有的细节模拟了美国地下的地球研究小组制作的电影跟踪了移动阵列部署后出现的色散图，并定期在EarthScope审查会议上放映。拟议研究的结果也将被视为实现美国地震学界对EarthScope愿景的重要组成部分。