GeoPRISMS Postdoctoral Scholar: Refining GPS-Acoustic Processing to Measure Cascadia Subduction

GeoPRISMS 博士后学者：改进 GPS 声学处理以测量卡斯卡迪亚俯冲带

• 批准号: 1850685
• 负责人: David Schmidt
• 金额: $ 26.03万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-05-01 至 2022-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1850685&HistoricalAwards=false
• 关键词: GeoPRISMS; Postdoctoral; Scholar; Refining; GPS

There is geologic and historical evidence that a magnitude 9.0 earthquake, comparable in size to the earthquake off Japan in 2011, could strike the Cascadia subduction zone, the region immediately offshore Oregon and Washington State where the ocean floor is slowly crashing into and sinking below the North American continent. Normally when assessing seismic hazards on land, the movement of the ground is measured using the Global Positioning System (GPS), which informs where an earthquake may happen in the future and how large it may be. However, GPS can not be used in offshore regions like the Cascadia subduction zone because a seafloor instrument cannot directly communicate with an orbiting satellite through the water column. Instead, an analogous technique called GPS-Acoustic is used. GPS-Acoustic couples the satellite signals from GPS with sound waves from instruments deployed on the seabed to measure the movement of the seafloor. However, GPS-Acoustic instruments are not as accurate as onshore GPS stations because of difficulties in predicting how fast sound will travel through the ocean at any specific time and place. This project seeks to use improved oceanographic models of sound speed to improve measurements of seafloor movement along the Cascadia subduction zone. This will in turn allow a more accurate assessment of the seismic hazard in the region. Broader impacts of the work include the support of a postdoctoral scholar, potential improvements in subduction-zone seismic hazard assessments and potential cross-disciplinary impact for both geodesy and physical oceanography.The goal of the project is to test the assumptions of a stationary and horizontally layered sound velocity structure for GPS-Acoustic positioning. Oceanographic hindcast models will be used to inform a strategy to filter out the variations in sound velocity from the GPS-Acoustic residuals. This will allow implementation of methods to more accurately and efficiently isolate the geologic and oceanographic signal in the travel time residuals collected during GPS-Acoustic deployment. This approach will be evaluated using GPS and acoustic ranging data previously collected by a Wave Glider for sites above the Cascadia subduction zone. If successful, the accuracy of GPS-Acoustic displacement measurements will be improved from the cm-scale to the mm-scale, as well as the efficiency of GPS-Acoustic by shortening the required data collection window. With improved GPS-Acoustic measurements, refined boundary conditions will be generated for fault locking models along the Cascadia margin and aid in the monitoring of the seismic cycle, in line with the goals of the GeoPRISMS initiative to improve understanding of subduction cycles and deformation.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.

有地质和历史证据表明，在2011年的地震大小相当的9.0级地震可能会袭击卡斯卡迪亚俯冲带，该地区立即在俄勒冈州近海和华盛顿州，那里的海底慢慢坠入并沉没在北美大陆以下。通常，在评估土地上的地震危害时，使用全球定位系统（GPS）来衡量地面的运动，该系统告知地震将来可能发生地震以及它的大小。但是，由于海底仪器无法通过水柱直接与轨道卫星通信，因此无法在海上区域中使用GP。取而代之的是，使用了一种称为GPS声学的类似技术。 GPS声学夫妇来自GPS的卫星信号，并在海床上部署了来自仪器的声波，以测量海底的运动。但是，由于难以预测在任何特定的时间和地点，GPS声学仪器都不像陆上GPS站那样准确。该项目旨在利用改进的声速海洋学模型来改善卡斯卡迪亚俯冲带的海底运动的测量。 反过来，这将允许对该地区的地震危害进行更准确的评估。这项工作的更广泛影响包括支持博士后学者，俯冲区的地震危险评估的潜在改善以及对地球和物理海洋学的潜在跨学科影响。该项目的目的是测试GPS-OusoStic sopstic soptictictions的固定和水平分层声音结构的假设。 海洋学后广播模型将用于告知一种策略，以滤除GPS声学残差的声音速度变化。 这将允许实施方法，以更准确有效地分离GPS声学部署期间收集的旅行时间残差中的地质和海洋信号。 将使用GPS和声学范围的数据评估这种方法，这是由波滑翔机在卡斯卡迪亚俯冲带上方的地点收集的。如果成功，通过缩短所需的数据收集窗口，将将GPS声学位移测量的准确性从CM规模提高到MM尺度。 随着GPS声学测量的改进，将为沿卡斯卡迪亚利润的故障锁定模型产生精致的边界条件，并有助于监视地震周期，这符合地理化主义计划的目标，以提高对俯冲周期的理解和对变形的理解，这反映了NSF的智力及其依据，这表明了NSF的合法任务和构建的依据，这是依据的范围。 标准。