A long-lived deep-water continuously operating reference station for seafloor geodesy

海底大地测量测量地球在水下的运动。目前的技术通过从海面向海底发送和接收信号并返回来接收来自海底仪器的数据。然而，这种方法具有~3000 m的深度限制，这极大地限制了可以部署仪器的位置。该项目使用一种不同的技术进行研究，该技术可用于深水，只需要信号从海面传播到海底。更广泛的影响包括支持一名研究生和与一家工程公司合作。海底大地测量仍然是地球物理学的前沿领域。在长时间和长空间基线范围内对海底位置和位移进行高精度测量，是解决各种一级重要科学问题的关键，例如俯冲带和其他地震成核地区的长期行为。该项目利用在5 225米深水中进行的实地实验获得的数据，测试全球导航卫星系统声学海底大地测量的新方法。全球导航卫星系统-声学大地测量系统（1）直接在海底（而不是虚拟点）上定位一个物质点（称为C-DOG的连续深海大地测量传感器），（2）通过海底信标使用单向声学走时测量，（3）可以快速连续测量多个C-DOG的非静止水面船只。(4)它还利用了GNSS处理技术的最新发展，用于声换能器的精确点定位，（5）它能够在海底长时间保持休眠，（6）作为反演策略的一部分，它校正了由于声速误差引起的偏差。劳动力发展包括一名研究生，他将与工程合作伙伴密切互动，以发展必要的专业知识。该奖项反映了NSF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。

Seafloor geodesy measures motion of the earth underwater. Current technology receives data from seafloor instruments by sending and receiving signals from the sea surface to the seafloor and back. However, this method has a depth limitation of ~3000 m which greatly limits where instruments can be deployed. This project investigates using a different technique which can be used in deep water that only requires the signals to travel from the sea surface to the seafloor. Broader impacts include support for a graduate student and partnering with an engineering company.Seafloor geodesy remains a frontier area of geophysics. Suboceanic measurements of position and displacement made with high precision over long spatial and long temporal baselines hold the key to a variety of scientific questions of first-order importance, such as the long-term behavior of subduction zones and other areas where earthquakes nucleate. This project tests a new approach to GNSS-Acoustic seafloor geodesy using data from a field experiment acquired in 5225 m deep water. The system of GNSS-Acoustic geodesy (1) directly positions a material point (a Continuous Deep Ocean Geodetic sensor called C-DOG) on the seafloor (rather than a virtual point), (2) uses a one-way acoustic travel-time measurement by the seafloor beacon and (3) a non-stationary surface vessel that can survey multiple C-DOGs in rapid succession. (4) It furthermore leverages recent developments in GNSS processing techniques for precise point positioning of the acoustic transducer, (5) it is capable of remaining dormant on the seafloor for an extended time, and (6) it corrects for bias due to sound velocity errors as part of the inversion strategy. Workforce development includes a graduate student who will interact closely with engineering partners to develop the necessary expertise. Educational materials for outreach developed during this project will be widely shared to the scientific community.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.