Collaborative Research: Near-Trench Community Geodetic Experiment

合作研究：海沟附近社区的大地测量实验最大的地震(及其引发的海啸)发生在海上，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对近海地震危险性进行量化。研究这些危险需要设计用于收集离岸数据的工具。一种这样的工具是GNSS-声学方法，这是一种海上GPS(全球定位系统)方法，将成套仪器以圆形分组设置在海底。这些仪器是相对于使用声音脉冲的遥控海面机器人进行定位的。这种“波浪滑翔机”可以使用GPS来确定其位置，从而使海底仪器的定位精度达到厘米级。随着时间的推移跟踪这些位置，研究人员可以了解变形的海底是如何积累压力，最终导致地震的。该项目遵循了一大批科学家的建议，他们有兴趣了解随着海底地壳逐渐滑入大陆地壳之下，俯冲带中的海底是如何变形的。该项目旨在探测卡斯卡迪亚近海地区和阿拉斯加近海地区的六个海底观测站的海底运动。这将有助于科学界评估这些地区的地震和海啸危害。这些数据都将开放获取，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，在那里海底的大垂直位移可能会产生破坏性的海啸。该项目将通过使用海底大地测量来推断卡斯卡迪亚和阿拉斯加俯冲带吸积棱柱中储存的弹性应变水平，从而阐明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。研究人员将在海底大地测量社区池中部署全球导航卫星系统声学仪器，该池由51个全球导航卫星系统声波应答器(足以容纳17个新的全球导航卫星系统声学站点)和3个波浪滑翔机组成，这是参加海底大地测量社区讲习班的165名科学家和学生就如何最好地利用仪表池提出的建议。在这次试验期间将建立12个新的全球导航卫星系统声学站点，沿着卡斯卡迪亚和阿拉斯加俯冲带海沟各6个，讲习班与会者将这些海沟确定为高价值的科学目标。研究人员将在该项目的五年期间，每年对这些新的地点以及这些地区已经建立的七个地点进行调查。这些位置将被用来推断地震间的速度，由此可以确定增量棱柱中的弹性应变积累率，这将对阿拉斯加和太平洋西北部的地震和海啸危险产生影响。这些数据都将是开放获取的，该项目将有助于培训下一代大地科学家。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.