Collaborative Research: Near-Trench Community Geodetic Experiment

合作研究：近海沟社区大地测量实验最大的地震（以及由此产生的海啸）发生在近海，但传统上用于研究与这些事件相关的地面变形的仪器只能在陆地上使用。因此，传统测量无法量化近海地震危害。研究这些危害需要专门用于收集海上数据的工具。其中一个工具是 GNSS-Acoustic 方法，这是一种海上 GPS（全球定位系统）方法，在海底以圆形分组方式设置多组仪器。这些仪器使用声音脉冲相对于遥控海面机器人定位。这种“波浪滑翔机”可以使用 GPS 来确定其位置，从而使海底仪器能够以厘米级的精度进行定位。随着时间的推移跟踪这些位置可以让研究人员了解变形的海底如何产生压力，最终导致地震。该项目遵循了一大群科学家的建议，这些科学家有兴趣了解当海底地壳逐渐滑到大陆地壳下方时，俯冲带中的海底如何变形。该项目旨在探测卡斯卡迪亚近海地区的六个站和阿拉斯加近海地区的六个站的海底运动。这将有助于科学界评估这些地区的地震和海啸灾害。这些数据将全部开放，该项目将有助于培训下一代大地测量科学家。2011 年东北地震表明，同震破裂可以沿着俯冲巨型逆冲延伸到浅层深度，海底的巨大垂直位移可能会产生破坏性海啸。该项目将通过利用海底大地测量观测来推断卡斯卡迪亚和阿拉斯加俯冲带增生棱镜中存储的弹性应变水平，从而澄清卡斯卡迪亚和阿拉斯加近海地区是否会发生类似的事件。研究人员将根据参加海底大地测量社区研讨会的 165 名科学家和学生关于如何最好地利用仪器池的建议，部署来自海底大地测量社区池的 GNSS 声学仪器，该池由 51 个 GNSS 声学转发器（足够 17 个新的 GNSS 声学站点）和 3 个波浪滑翔机组成。本次实验期间将建立 12 个新的 GNSS 声学站点，其中卡斯卡迪亚和阿拉斯加俯冲带海沟各有 6 个，研讨会与会者将其确定为高价值的科学目标。在该项目的五年内，研究人员将每年对这些新站点以及这些地区已建立的七个站点进行调查。这些位置将用于推断震间速度，从而确定吸积棱柱中弹性应变累积的速率，这对阿拉斯加和太平洋西北地区的地震和海啸灾害具有影响。这些数据将全部开放获取，该项目将有助于培训下一代大地测量科学家。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Collaborative Research: Near-Trench Community Geodetic ExperimentThe largest earthquakes (and the resulting tsunamis) occur offshore, but the instruments traditionally used to study the ground deformation associated with these events can only be used on land. Therefore, traditional surveying cannot quantify the offshore seismic hazards. Studying these hazards requires tools designed to collect data offshore. One such tool is the GNSS-Acoustic method, an offshore GPS (Global Positioning System) method with sets of instruments set up on the seafloor in circular groupings. These instruments are positioned relative to a remote-controlled sea surface robot using sound pulses. This ‘Wave Glider’ can use GPS to determine its position, allowing the seafloor instruments to be located with cm-level accuracy. Tracking these positions over time allows researchers to learn how the deforming seafloor builds up stress that ultimately results in earthquakes. This project follows recommendations by a large group of scientists who are interested in knowing how seafloor deforms in subduction zones as the seafloor crust gradually slides beneath the continental crust. The project aims to detect the motions of the seafloor at six stations in the offshore Cascadia region and six in the offshore Alaska region. This will aid the scientific community in assessing the seismic and tsunami hazards in these regions. The data will all be open access and the project will contribute to training the next generation of geodetic scientists.The 2011 Tohoku earthquake demonstrated that coseismic rupture can extend to shallow depths along a subduction megathrust, where large vertical displacements of the seafloor can generate damaging tsunamis. This project will clarify whether a similar event can happen in the offshore Cascadia and Alaska regions by using seafloor geodetic observations to infer the level of elastic strain stored in the accretionary prisms of Cascadia and Alaska subduction zones. The researchers will deploy GNSS-Acoustic instruments from the seafloor geodesy community pool, which consists of 51 GNSS-Acoustic transponders (enough for 17 new GNSS-Acoustic sites) and 3 Wave Gliders, following recommendations from 165 scientists and students who attended a seafloor geodesy community workshop on how best to make use of the instrument pool. Twelve new GNSS-Acoustic sites will be established during this experiment, with six along each of the Cascadia and Alaska subduction zone trenches, which were identified by workshop attendees as high-value science targets. The researchers will survey these new sites as well as the seven sites already established in these regions annually throughout the five years of the project. These positions will be used to infer interseismic velocities from which the rate of elastic strain buildup in the accretionary prisms can be determined, with implications for the earthquake and tsunami hazard in Alaska and the Pacific Northwest. The data will all be open access and the project will contribute to training the next generation of geodetic scientists.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.