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，利用国家科学基金会赞助的研究船上现有的多波束声纳，测量与地震和山体滑坡等快速事件相关的海底小位移。海底位移是通过比较一个事件中两次调查的一片海底的位置来测量的。这种方法的公开精度目前是几十米，这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，使其优于1米，方法是以慢速收集数据，并在重复航迹上导航，使其紧紧跟随参考航迹。位移精度的这一数量级改进将为评估和了解大型和有时具有破坏性的海底事件提供一个宝贵的工具。更广泛的影响包括对系统软件的改进，这些软件将免费提供给其他人。该项目将开发一种方法，利用国家科学基金会赞助的研究船上现有的多波束声纳，测量与地震和滑坡等快速事件相关的海底微小位移。海底位移是通过对一个事件中两次测量的一片海底位置进行差分来测量的。这种方法的公开精度目前是几十米，这严重限制了该方法的实用性。这项工作将大大提高精度，通过以低速收集数据和导航重复轨迹以密切跟踪参考轨迹，将精度提高到1米以上。位移精度的这一数量级改进将为评估和了解大型和有时具有破坏性的海底事件提供一个宝贵的工具。该提案解决了最近的国家研究委员会十年报告（NRC，2015）中提出的八个高级科学问题之一，即， 如何更好地描述风险，如何提高预测特大地震、海啸、海底滑坡和火山爆发等地质灾害的能力？全球定位系统和干涉合成孔径雷达的工具被用来监测卡斯卡迪亚俯冲带陆上的地壳变形，但大部分的锁定部分的巨型逆冲断层接口位于海上。当PI？的方法没有足够的精度来监测地震间运动，它可以作为一个类似于圣安德烈亚斯断层B-4激光雷达调查的地表跟踪事件前的调查。

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.