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活动的例子，火山活动和地震发生在远离板块边界的地方。然而，对于控制这条5800公里长、0-80 Ma的岩浆链上的岩浆活动和地震活动的基本过程，人们仍然存在疑问，部分原因是人们对加入太平洋地壳表面和底部的冻结岩浆的体积和成分知之甚少。这项研究的目的是使用“最先进的”海洋地震成像技术来限制夏威夷热点产生的岩浆物质的厚度和组成，它如何沿着海山链变化，以及太平洋板块如何响应火山负荷而变形。这项研究是与Lamont-Doherty地球天文台的美国科学家合作进行的，将利用在以前的研究巡航（例如R/V Robert D. Conrad C2308， R/V Thomas Washington Roundabout 2和R/V Maurice Ewing EW9801）上获得的再处理地震反射和折射数据，以及将在2018年夏末和2019年夏初在R/V Marcus G. Langseth上获得的新数据集。Langseth巡航由美国国家科学基金会（海洋地质和地球物理部）资助，将使用15公里长的拖带和大型调谐气枪阵列获得深穿透地震反射数据，并使用70个海底地震仪，沿4条500公里长的横断面间隔15公里获取广角反射/折射数据。这些样带位置经过精心选择，以代表岩浆就位和体积通量的时间变化、海洋岩石圈在加载时的年龄和板块中间地形膨胀的存在/不存在，并且足够长，可以捕捉岩石圈对火山加载到弯曲凸起的响应。再处理和处理后的地震反射剖面和广角地震数据建立的速度模型将约束地壳表面和底部岩浆添加物的体积和分布，侧面弯曲护城河地层填充物的性质以及弯曲火山构造和下伏海洋板块内断裂的相对作用。与其他热点岩浆活动的海洋地球物理研究相比，地震约束将与带状测深和势场数据相结合，并作为热学和力学建模的基础，以获得对地壳和岩石圈流变学和应力状态的基本见解，并为沿链的潜在地质灾害提供信息，如大规模斜坡破坏、断层滑动和海啸性地震。这里提出的研究是NERC战略的核心，特别是因为它涉及到影响地球如何工作的发现科学，它如何响应地表和地下载荷而变形，以及未来它可能如何变形。

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.