Collaborative Research: The Hawaiian PLUME Deployment in a Global Context

夏威夷远离任何板块边界的位置为检验地幔柱假说提供了绝佳的机会：来自地幔深处的热流是否会在地球上产生热点火山活动？年代的表面。“地幔柱-岩石圈海底融化实验”（PLUME）的初步地震成像，由陆地和海底地震仪的临时部署组成，揭示了第一张高分辨率的3d图像，证明了深锚地幔柱的存在。然而，PLUME地震记录尚未被充分利用。到目前为止，体波和面波数据集通常是独立分析的，现在必须联合建模。这将有助于区分温度异常（通常被认为是造成地震异常的原因）和其他原因（如岩石成分或机械强度的变化）。这项研究的另一部分是了解夏威夷地震波如何衰减，该项目将从地震记录中提取新的衰减数据。我们还将通过将PLUME数据集嵌入到全局模型中，将其置于全局上下文中。全球断层扫描可以解决对羽流数据集的孤立解释无法提供的基本问题：夏威夷羽流是否在核心-地幔边界附近有自己的孤立起源，还是起源于中太平洋的大型低剪切速度省？目前在区域体波图像中成像的深地幔异常倾斜是一个在全球模型中持续存在的强大特征吗？软流层是否与东太平洋隆起存在联系，从而解释夏威夷玄武岩中发现的一些复杂化学物质？科学家们长期以来一直在争论，夏威夷、黄石公园或冰岛等热点地区是来自下地幔的热而浮力上涌的“地幔柱”的产物，可能起源于地幔核心边界深处，还是浅地幔过程的结果。地震研究可以帮助解决这些问题，因为地震波可以用来揭示地球？通过层析成像，探测高温区、地幔岩石异常区和熔融区。该项目将对夏威夷群岛周围和被称为夏威夷涌浪的海底隆起异常区域独特的陆地和海底地震仪（obs）部署的数据进行增强分析。先前对“羽流-岩石圈海底融化实验”（PLUME）的分析支持地幔羽流的存在，但需要更详细的研究来帮助回答一些基本问题，包括：夏威夷羽流是来自其自身在核心-地幔边界附近的孤立起源，还是来自太平洋中部大的低剪切速度省？烟羽实际上是一个连续的烟囱状特征，还是它分解成几个斑点？当前成像的地震异常倾斜是全球断层扫描模型中持续存在的强大特征吗？在地球较浅的软流圈中，是否存在与最近的主要洋中脊——东太平洋隆起——的联系，这就可以解释地球化学家在夏威夷熔岩中发现的一些复杂的化学物质？

Hawaii's location far from any plate boundary provides an excellent opportunity to test the plume hypothesis: whether hot upwellings from the deep mantle generate hotspot volcanism at the Earth?s surface. Initial seismic imaging for the "Plume-Lithosphere Undersea Melt Experiment" (PLUME), consisting of a temporary deployment of land and ocean bottom seismometers, has revealed the first high-resolution 3-D images that support the presence of a deep-anchored mantle plume. Yet, the PLUME seismic recordings have yet to be exploited to their fullest. The body and surface wave datasets that have so far been analyzed independently, as is usually the case, must be modeled jointly. This will help distinguish between temperature anomalies, which are usually assumed to cause seismic anomalies, and other causes such as changes in rock composition or mechanical strength. Another part of this research is the understanding of how seismic waves attenuate beneath Hawaii, and this project will extract new attenuation data from the seismic records. We will also place the PLUME dataset in a global context by embedding it in a global model. Global tomography can address fundamental questions that an isolated interpretation of the PLUME dataset cannot provide: Does the Hawaiian plume have its own isolated origin near the core-mantle boundary or does it originate from the large low shear-velocity province in the Central Pacific? Is the currently imaged tilt of the deep mantle anomaly in the regional body wave images a robust feature that persists in a global model? Does a connection with the East Pacific Rise exist in the asthenosphere that would explain some of the complex chemistry found in Hawaii's basalts?Scientists have long debated whether hotspots such as Hawaii, Yellowstone, or Iceland are the product of hot, buoyant upwelling "mantle plumes" from the lower mantle, perhaps originating as deep as the core mantle boundary, or are rather the result of processes in the shallow mantle. Seismic studies can help resolve such questions, because seismic waves can be used to reveal Earth?s internal structure through tomographic images and detect regions of high temperatures, mantle rock anomalies and melt. This project will perform enhanced analyses of data from a unique deployment of land and ocean bottom seismometers (OBSs) around the Hawaiian Islands and across the anomalous region of uplifted seafloor known as the Hawaiian Swell. Prior analyses of this deployment for the "Plume-Lithosphere Undersea Melt Experiment" (PLUME), support the presence of a mantle plume, but more detailed studies are needed to help answer fundamental questions, including: Does the Hawaiian plume originate from its own isolated origin near the core-mantle boundary or does it originate from the large low shear-velocity province in the Central Pacific? Is the plume in fact a continuous chimney-like feature or does it break up into several blobs? Is the currently imaged tilt of the seismic anomaly a robust feature that persists in a global tomography model? Does a connection with the nearest major mid-ocean ridge, the East Pacific Rise, exist in Earth's shallower layer known as the asthenosphere, which would explain some of the complex chemistry that geochemists have found in Hawaii's lavas?