Seismic imaging of lithospheric flexure along the Hawaiian-Emperor Seamount Chain and its implications for plate mechanics and mantle dynamics

夏威夷-皇帝海山链可以说是世界上最著名的热点岩浆作用的例子，火山活动和地震发生在远离板块边界的地方。然而，关于控制这条长沿着5 800公里、距今0-80 Ma的岛链上的岩浆活动和地震活动的基本过程，仍然存在疑问，部分原因是人们对太平洋洋壳表面和底部的冰冻岩浆的体积和成分知之甚少。本研究的目的是使用“最先进的”海洋地震成像技术来约束夏威夷热点所产生的岩浆物质的厚度和成分，它是如何沿沿着海山链变化的，以及太平洋板块是如何变形以应对火山负荷的。这项研究是与拉蒙特-多尔蒂地球观测站的美国科学家合作进行的，将利用以前研究航行中获得的再处理地震反射和折射数据（例如R/V Robert D.康拉德C2308，R/V托马斯华盛顿环岛2，和R/V莫里斯尤因EW 9801），连同一个新的数据集，将获得船上R/V马库斯G。2018年夏末和2019年初夏的Langseth。Langseth号巡航考察由国家科学基金会（海洋地质和地球物理司）资助，将利用15公里长的拖缆和大型调谐气枪阵列获取深穿透地震反射数据，并利用沿沿着4条500公里长的断面分布的、间隔15公里的70个海底地震仪获取广角反射/折射数据。样带的位置经过精心选择，以代表岩浆侵位和体积通量的时间，在加载时的海洋岩石圈的年龄和存在/不存在的中板地形隆起的变化，并有足够长的时间来捕捉岩石圈的反应，火山加载到弯曲隆起。从广角地震数据建立的再加工和处理的地震反射剖面和速度模型将限制地壳表面和底部的岩浆添加物的数量和分布、侧翼弯曲护城河中地层填充物的性质以及弯曲火山建筑物和下面的海洋板块内断层的相对作用。地震制约因素将与条带测深和势场数据相结合，与热点岩浆活动的其他海洋地球物理研究相比较，并用作热力和力学建模的基础，以便从根本上了解地壳和岩石圈的流变和应力状态，并告知沿着链的潜在地质灾害，如大规模斜坡破坏、断层滑动和海啸地震。这里提出的研究是NERC战略的核心，特别是因为它涉及发现科学，影响行星地球如何工作，它如何响应表面和地下负荷而变形，以及它未来可能如何变形。

The Hawaiian-Emperor Seamount Chain is arguably the world's best known example of hotspot magmatism, where volcanic activity and earthquakes occur far from plate boundaries. Nevertheless, questions remain about the fundamental processes that control such magmatism and seismicity along the 5800-km-long, 0-80 Ma, chain, in part because the volume and compositions of frozen magma that has been added to the surface and base of Pacific oceanic crust is too poorly known. The aim of this study is to use 'state of the art' marine seismic imaging techniques to constrain the thickness and composition of the magmatic material created by the Hawaiian hotspot, how it varies along the seamount chain, and how the Pacific oceanic plate has deformed in response to volcano loading. This study, which is a collaborative one with US scientists at Lamont-Doherty Earth Observatory, will utilize reprocessed seismic reflection and refraction data acquired on previous research cruises (e.g. R/V Robert D. Conrad C2308, R/V Thomas Washington Roundabout 2, and R/V Maurice Ewing EW9801), together with a new data set that will be acquired onboard R/V Marcus G. Langseth during late summer, 2018 and early summer, 2019. The Langseth cruises, which have been funded by the National Science Foundation (Marine Geology and Geophysics Division), will acquire deep penetration seismic reflection data using a 15 km long streamer and a large tuned airgun array and wide-angle reflection/refraction data using 70 Ocean Bottom Seismometers spaced at 15 km intervals along four 500-km-long transects of the chain. The transect locations have been carefully chosen to represent variations in the timing of magma emplacement and volume flux, the age of oceanic lithosphere at the time of loading and the presence/absence of a mid-plate topographic swell, and are sufficiently long to capture the response of the lithosphere to volcano loading out to the flexural bulge. The reprocessed and processed seismic reflection profiles and velocity models created from wide-angle seismic data will constrain the volume and distribution of magmatic addition to the surface and base of the crust, the nature of the stratigraphic fill in the flanking flexural moats and the relative role of faulting within the flexed volcanic edifice and underlying oceanic plate. The seismic constraints will be integrated with swath bathymetry and potential field data, compared to other marine geophysical studies of hotspot magmatism and used as the basis for thermal and mechanical modeling in order to gain fundamental insights into crust and lithosphere rheology and stress state and to inform potential geohazards along the chain such as large-scale slope failures, fault slip and tsunamigenic earthquakes. The study proposed here is central to NERC's strategy especially as it involves discovery science that impacts on how planet Earth works, how it deforms in response to surface and sub-surface loads and how it might deform in the future.