Seafloor Geodesy Using Sidescan Sonar: Analysis of the NGDC Archive

该项目的主要目标是开发一种方法，利用现有的多波束声纳（可在nsf资助的研究船上使用）来测量与地震和滑坡等快速事件相关的海底小位移。海底位移是通过比较在一次事件中两次测量的一块海底的位置来测量的。目前已公布的该方法的精度为几十米，严重限制了该方法的实用性。计划中的工作将大大提高精度，以慢航速收集数据，并在重复航迹上航行，密切跟随参考航迹，精度将提高到1米以上。位移精度的这一数量级提高将为评估和理解大型、有时具有破坏性的海底事件提供有价值的工具。更广泛的影响包括系统软件的改进，这些改进将免费提供给其他人。资金包括培训一名高分辨率声纳和海底大地测量方法的研究生。该项目将开发一种方法，利用现有的多波束声纳（可在nsf资助的研究船上使用）来测量与地震和滑坡等快速事件相关的海底小位移。海底位移是通过在跨越一个事件的两次测量中不同的海底块的位置来测量的。目前已公布的该方法的精度为几十米，严重限制了该方法的实用性。通过以慢航速采集数据，并在重复航迹上紧密跟随参考航迹，将精度大大提高到1米以上。位移精度的这一数量级提高将为评估和理解大型、有时具有破坏性的海底事件提供有价值的工具。该提案解决了最近的国家研究委员会十年报告（NRC, 2015）中提出的八个高水平科学问题之一，即如何更好地表征风险，并提高对特大地震、海啸、海底滑坡和火山爆发等地质灾害的预测能力？GPS和InSAR工具用于监测卡斯卡迪亚俯冲带陆上的地壳变形，但大逆冲界面的大部分锁定部分位于海上。而PI呢？虽然该方法的精度不足以监测地震间运动，但它可以作为类似于圣安德烈亚斯断层B-4激光雷达测量的地表轨迹的事件前测量。

The main objective of the project is to develop a method to use existing multibeam sonars, available on NSF-sponsored research vessels, to measure small displacements of the seafloor associated with rapid events such as earthquakes and landslides. The seafloor displacements are measured by comparing the location of a patch of seafloor surveyed at two times spanning an event. The published accuracy of this approach is currently tens of meters which severely limits the utility of the method. The planned work would greatly improve the accuracy to better than 1 m by collecting data at a slow ship speed and navigating the repeat track to closely follow the reference track. This order of magnitude improvement in displacement accuracy would provide a valuable tool for assessing and understanding large and sometimes-destructive seafloor events. Broader impacts include improvements to the system software that will be freely available to others. Funding includes the training of a graduate student in the methods of high-resolution sonar and seafloor geodesy.The project will develop a method to use existing multibeam sonars, available on NSF-sponsored research vessels, to measure small displacements of the seafloor associated with rapid events such as earthquakes and landslides. The seafloor displacements are measured by differencing the location of a patch of seafloor surveyed at two times spanning an event. The published accuracy of this approach is currently tens of meters which severely limits the utility of the method. This work would greatly improve the accuracy to better than 1 m by collecting data at a slow ship speed and navigating the repeat track to closely follow the reference track. This order of magnitude improvement in displacement accuracy would provide a valuable tool for assessing and understanding large and sometimes-destructive seafloor events. The proposal addresses one of the eight high-level science questions posed in the recent National Research Cpuncil Decadal Report (NRC, 2015), i.e., how can risk be better characterized and the ability to forecast geohazards like mega-earthquakes, tsunamis, undersea landslides, and volcanic eruptions be improved? The tools of GPS and InSAR are used to monitor the crustal deformation onshore of the Cascadia Subduction Zone but most of the locked part of the megathrust interface lies offshore. While the PI?s method does not have sufficient accuracy to monitor interseismic motions, it can serve as a pre-event survey of the surface trace similar to the San Andreas Fault B-4 lidar survey.