Global P, SV, and converted wave measurements for improved lower mantle P and S structure studies

这一提议旨在测量地球仪记录的地震图上每一个可能观测到的地震波。 测量所有可能的波包括记录它们的旅行时间和波形信息。 然后，这些数据可以用于支持地球地幔的地震成像工作，这些工作目前通常不使用波的多次反弹或回波，特别是P波。使用这些波可以确保更好地采样地球地幔的整个体积。 除此之外，南半球的采样率特别低。 更好地成像地球地幔是重要的，因为它允许更准确地确定地震属性以及驱动地球表面板块构造的内部动态对流。一个完整的地震波子集的数据集将允许基准不同的研究小组的层析模型，以及允许更直接的比较P和S波模型的深地幔的显着不均匀性。 特别是，这项工作将研究两个巨大的低地震波速度结构：一个在太平洋下面，一个在大西洋和非洲下面。 这些巨大的结构是地球上最大的异常，在自然界中是未知的。 生成的模型将以3D形式呈现，并通过亚利桑那州立大学的3D马斯顿剧院与公众分享，该剧院定期向公众展示科学。 该项目还将支持和培训亚利桑那州立大学的两名学生。 培训本科生将涉及创建和定期更新数据敏锐度培训文档，该文档也将通过网络共享。学生将参与数据分析，解释和撰写论文发表。 科学效果图（例如，该项目将测量和量化高质量P波相位、SV分量运动的S波相位、地幔中具有P和SV腿的相位以及P、SH、SV和P-SV波的深度相位的全球地震数据集的走时行为。所采用的方法结合了两种新的工具：（1）经验小波（EW）构造的平均形状的S和P波的事件的基础上，自适应地调整，以匹配可变脉冲宽度的数据，从而最大限度地减少旅行时估计误差;以及（2）从感兴趣的相位的站的局部地理箱栈构建的虚拟站，使得对于具有事件-站走廊的数据的测量成为可能，该事件-站走廊对于置信测量而言通常幅度太低。这里提出的新的地震测量将记录旅行时间沿着所有测量波形的几个属性，包括波形信息（振幅、波形宽度、与最佳拟合EW相比的波形失配）、信噪比（SNR，多路测量）和互相关系数（CCC，感兴趣的相位和最佳拟合EW之间）。研究人员将在相对较短的时间内（10-16秒）测量次要和主要电弧数据。新的数据集旨在提高地幔P和S地震成像的分辨率，目的是提高对地球结构、动力学和演化的理解。这些数据将改善南半球的波径覆盖范围，适用于整个地幔的成像研究，并与最近使用相同方法完成的SH数据集一起沿着公开提供。这些数据将用于成像大低速区，重点是比较P和S速度非均匀性，这与非均匀性的性质有关。这项工作将资助一名博士生和一名本科生收集、处理、测量和审查P和SV地震数据。PI将指导学生在地幔异质性的多学科性质，特别是地幔的动力学和演化的更广泛的视角，与亚利桑那州立大学的多学科地球物理学组（地震学，矿物物理学，地球动力学和行星地球物理学）的参与。所有的数据测量、模型和代码都将通过网络以及IRIS的断层扫描模型门户网站与社区公开共享。 所有测量结果将与三维参考地球模型项目共享。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This proposal seeks to measure every possible observable seismic wave on seismograms recorded across the globe. Measuring all possible waves involves documenting their travel times and wave shape information. These data can then be used to bolster seismic imaging efforts of Earth's mantle which currently do not routinely use multiple bouncing or echoing of waves, especially P waves. Using these waves ensures better sampling of the entire volume of the Earth's mantle. Otherwise, the southern hemisphere in particular is poorly sampled. Better imaging of Earth's mantle is important because it allows for more accurate determination of earthquake properties as well as the dynamic convection of the interior which drives plate tectonics at Earth's surface. A complete dataset of a subset of seismic waves will allow benchmarking tomographic models of different research groups, as well as permit a more direct comparison of P and S wave models of significant heterogeneities of the deep mantle. In particular, this work will study two massive low seismic wave speed structures: one beneath the Pacific Ocean, and one beneath the Atlantic Ocean and Africa. These huge structures are the largest anomalies in the planet which are unknown in nature. Resulting models will be rendered in 3D and shared with the public via the 3D Marston Theater at Arizona State University, which regularly gives science shows to the general public. The project will also support and train two students at ASU. Training the undergraduate student will involve the creation and regular updating of a data acumen training document, which will also be shared via the web. Students will be involved in data analysis, interpretation, and writing papers to be published. Scientific renderings (e.g., models and schematics) will be shared via the PI's website, as well as via direct email.This project will measure and quantify travel time behavior of a global seismic dataset of high quality P-wave phases, S-wave phases on the SV component of motion , phases having both P and SV legs in the mantle, and depth phases of P, SH, SV, and P-SV waves. The adopted approach incorporates two novel tools recently developed: (1) empirical wavelets (EWs) are constructed from the average shape of S and P waves on an event-by-event basis, which are adaptively adjusted to match variable pulse widths prevalent in data, thus minimizing travel time estimation errors; and (2) virtual stations which are built from localized geographical bin stacks of stations for phases of interest, making measurements possible for data with event-station corridors typically too low in amplitude for confident measurements. The new seismic measurements proposed here will document travel times along with several attributes of all measured waveforms, including wave shape information (amplitude, waveform broadness, waveform misfit compared to the best fitting EW), signal-to-noise ratios (SNRs, measured multiple ways), and cross-correlation coefficients (CCCs, between phases of interest and best-fitting EWs). The investigators will measure minor and major arc data at relatively short periods (10-16 sec). The new datasets aim to improve resolution in P and S seismic imaging of the Earth's mantle, with the goal of improving understanding of the structure, dynamics, and evolution of the Earth. These data will improve wave path coverage in the southern hemisphere, be applicable to imaging studies of the entire mantle, and be made publicly available along with a recently completed SH dataset using the same methodology. The data will be used for imaging large-low velocity provinces, with a focus on comparing P and S velocity heterogeneity, which bears upon the nature of heterogeneity. This work will fund a PhD student and an undergraduate student to collect, process, measure, and review P and SV seismic data. The PI will mentor the students within a broader perspective of the multidisciplinary nature of mantle heterogeneity, particularly the dynamics and evolution of the mantle, with participation in ASU's multidisciplinary geophysics group (seismology, mineral physics, geodynamics, and planetary geophysics). All data measurements, models, and codes will be openly shared with the community via the web, as well as IRIS's tomography model portal. All measurements will be shared with the 3D Reference Earth Model project.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.