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来测量与地震和山体滑坡等快速事件有关的海底小幅位移。海底位移是通过比较在一次事件中两次测量的海底斑块的位置来测量的。目前已公布的该方法的精度为几十米，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，通过在缓慢的船速下收集数据，并在重复航迹上导航，紧跟参考航迹，从而使精度提高到1米以下。位移精度的这种数量级提高将为评估和了解大型、有时具有破坏性的海底事件提供宝贵的工具。更广泛的影响包括对系统软件的改进，其他人将可以免费获得。资金包括对一名研究生进行高分辨率声纳和海底大地测量方法的培训。该项目将开发一种方法，利用美国国家科学基金会赞助的研究船上现有的多波束声纳来测量与地震和山体滑坡等快速事件有关的海底小位移。海底位移是通过在一次事件中两次测量海底斑块的位置差来测量的。目前已公布的该方法的精度为几十米，这严重限制了该方法的实用性。这项工作通过在缓慢的船速下采集数据，并通过重复航迹导航紧跟参考航迹，将大大提高精度，使其优于1m。位移精度的这种数量级提高将为评估和了解大型、有时具有破坏性的海底事件提供宝贵的工具。该提案解决了最近的国家研究报告十年报告(NRC，2015)中提出的八个高级别科学问题之一，即如何更好地描述风险并提高预测大地震、海啸、海底山体滑坡和火山喷发等地质灾害的能力？利用GPS和InSAR工具监测卡斯卡迪亚俯冲带的陆上地壳形变，但巨型逆冲界面的大部分锁定部分位于近海。虽然皮？S方法没有足够的精度来监测地震间的运动，但它可以作为一种类似于圣安德烈亚斯B-4断层激光雷达测量的震前地表轨迹测量。

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.