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，传统的测量方法无法量化海上地震灾害。研究这些危害需要专门设计的工具来收集海上数据。其中一种工具是gnss -声学方法，这是一种近海GPS（全球定位系统）方法，在海底按圆形分组设置了几套仪器。这些仪器相对于一个利用声脉冲遥控的海面机器人进行定位。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积聚压力，最终导致地震。这个项目遵循了一大批科学家的建议，他们对了解海底地壳在大陆地壳下逐渐滑动时海底是如何在俯冲带变形的感兴趣。该项目旨在探测卡斯卡迪亚近海地区的六个监测站和阿拉斯加近海地区的六个监测站的海底运动。这将有助于科学界评估这些地区的地震和海啸危害。这些数据将全部开放获取，该项目将有助于培养下一代大地测量科学家。2011年的东北地震表明，同震破裂可以沿着俯冲巨型逆冲带延伸到浅层，在那里海底的巨大垂直位移可以产生破坏性的海啸。该项目将通过海底大地测量观测来推断储存在卡斯卡迪亚和阿拉斯加俯冲带的吸积棱镜中的弹性应变水平，从而澄清类似的事件是否会发生在卡斯卡迪亚和阿拉斯加近海地区。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，研究人员将从海底大地测量社区池中部署gnss -声学仪器，其中包括51个gnss -声学转发器（足以用于17个新的gnss -声学站点）和3个波浪滑翔机。在本次实验中，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沟槽各6个，这些沟槽被研讨会与会者确定为高价值的科学目标。研究人员将在项目的五年中每年对这些新地点以及在这些地区已经建立的七个地点进行调查。这些位置将用于推断地震间速度，由此可以确定增生棱镜中弹性应变积累的速率，并对阿拉斯加和太平洋西北部的地震和海啸危险产生影响。这些数据将全部开放获取，该项目将有助于培养下一代大地测量科学家。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.