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羽流假说提供了一个绝佳的机会：地幔深处的热上涌是否会在地球表面产生热点火山活动？S。由临时部署陆地和海底地震仪组成的“羽流-岩石圈海底熔融实验”(羽流)的初步地震成像揭示了第一批高分辨率三维图像，这些图像支持深部锚定地幔羽流的存在。然而，羽流地震记录还没有得到最充分的利用。像通常情况一样，迄今独立分析的体波和面波数据集必须联合建模。这将有助于区分温度异常和其他原因，如岩石成分或机械强度的变化。温度异常通常被认为是导致地震异常的原因。这项研究的另一个部分是了解夏威夷下面的地震波是如何衰减的，这个项目将从地震记录中提取新的衰减数据。我们还将通过将羽流数据集嵌入到全局模型中，将其放置在全局环境中。全球层析成像可以解决对羽流数据集的孤立解释无法提供的基本问题：夏威夷羽流是在核-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的低剪切速度省？目前在区域体波图像中成像的深部地幔异常的倾斜是在全球模式中持续存在的稳健特征吗？软流圈中是否存在与东太平洋隆起的联系，这可以解释夏威夷玄武岩中发现的一些复杂的化学物质？长期以来，科学家们一直在争论，夏威夷、黄石或冰岛等热点是来自下地幔的热的、有浮力的上涌地幔热柱的产物，或许起源于地核地幔边界深处，或者更确切地说，是浅地幔过程的结果。地震研究可以帮助解决这样的问题，因为地震波可以通过层析图像揭示地球S的内部结构，并探测高温、地幔岩石异常和熔融的地区。该项目将对夏威夷群岛周围独特部署的陆地和海底地震仪(OBSS)以及在被称为夏威夷隆起的海底异常区域的数据进行强化分析。先前对“羽流-岩石圈海底熔融实验”(羽流)这一部署的分析支持地幔羽流的存在，但需要进行更详细的研究以帮助回答基本问题，包括：夏威夷羽流是源自其自身在核-地幔边界附近的孤立起源，还是源自中太平洋的大的低剪切速度省？烟羽实际上是一个连续的烟囱状特征，还是会分裂成几个斑点？目前成像的地震异常倾斜是全球层析成像模型中持续存在的稳健特征吗？在地球上被称为软流圈的较浅层中，是否存在与最近的主要大洋中脊--东太平洋隆起--的联系，这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?