Collaborative Research: Vertical seafloor geodesy to accurately image slow slip events in a noisy ocean environment

合作研究：垂直海底大地测量以准确成像嘈杂海洋环境中的慢滑事件

• 批准号: 2140657
• 负责人: Spahr Webb
• 金额: $ 138.24万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-01 至 2026-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2140657&HistoricalAwards=false
• 关键词: Collaborative; Research; Vertical; seafloor; geodesy

The largest and most dangerous earthquakes are subduction zone earthquakes where the source of the earthquake is almost completely underwater. The size of an earthquake and the propensity of an earthquake to create large dangerous tsunamis is determined by variations in the plate interface coupling which creates locked and unlocked regions of the fault. Understanding these variations in plate coupling is critical to understanding these dangerous earthquakes. Strain is released along some offshore parts of fault interfaces in occasional slow slip events (SSEs) where the fault moves much as with a normal earthquake, but the stored energy is released so slowly that these events are barely or not detectable on land. Regions between the SSE regions may remain locked, producing the potential for large tsunamigenic earthquakes. There is some evidence that SSEs on one part of a plate interface may increase strain on adjacent parts, triggering large earthquakes. Seafloor pressure gauges can detect SSEs as the seafloor moves upward during a SSE, decreasing the depth of the gauge. A SSE was detected and mapped in the proposed study region offshore New Zealand in 2015 using pressure gauges, as this is currently the only feasible method appropriate for wide application offshore. Those observations were greatly limited by the effects of oceanographic noise from ocean eddies. A much larger experiment is now planned for the same region. By adding oceanographic observations of near-seafloor current and vertical echo sounder data, the research should show this noise source can be much reduced and therefore reveal the spatial and temporal extent of offshore SSEs in greater detail and with better accuracy, improving our understanding of plate coupling relevant to understanding great earthquakes. The project will train a graduate student and postdoctoral researcher and involve them in a large international experiment. During this large collaborative experiment with New Zealand and Japanese scientists, a large array of ocean bottom geodetic, oceanographic, and seismological instruments will be deployed for two years offshore of the east coast of New Zealand's North Island, where one or more shallow SSEs are expected to occur during the deployment. The joint array would include 44 seafloor absolute pressure gauges (APGs) and 12 current meters and upward looking sonars to test and develop innovative methods to remove contaminating pressure variations that arise within the water column (labeled oceanographic noise). The reduced-noise seafloor data will enable more accurate description of the spatio-temporal evolution of offshore slow-slip events (SSEs). For the first time, an array of 11 APG sensors equipped with a system for removing long term drift from sensor data will be deployed, with potential long term benefit for oceanographic observations and for applying seafloor vertical geodesy at tectonic strain rates. Data from 21 ocean bottom seismometers in the combined array will be used to probe the relationship between earthquakes and tremor and seafloor SSEs. These observations will advance our understanding of offshore variations in plate coupling in subduction zones.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.

最大，最危险的地震是俯冲带地震，地震几乎完全在水下。地震的大小和地震倾向造成大型危险海啸的倾向取决于板界面耦合的变化，从而形成了断层的锁定和解锁区域。了解板耦合中的这些变化对于理解这些危险的地震至关重要。应变沿故障界面的某些离岸部分释放，偶尔发生慢滑动事件（SSE），在该事件中，断层移动的移动程度与正常地震一样，但是储存的能量的释放速度如此之缓慢，以至于这些事件在陆地上几乎无法检测到。 SSE区域之间的区域可能仍锁定，从而产生了大型海啸地震的潜力。有证据表明，在板界面的一个部分上的SSE可能会增加相邻部分的应变，从而触发大地震。海底压力表可以在SSE期间海底向上移动时检测到SSE，从而减小了仪表的深度。 2015年，使用压力表在拟议的研究区域中检测并映射了SSE，因为这是目前唯一适合广泛应用海上应用的可行方法。 这些观察结果受到海洋涡流噪声的影响，极大地限制了这些观察结果。现在计划针对同一地区进行更大的实验。通过添加海洋学观察到近乎层状电流和垂直回声声音数据，该研究应表明该噪声源可以大大降低，因此可以更详细地揭示海上SSE的空间和时间范围，并以更好的准确性，提高我们对板块的理解，以了解与理解大地震相关的板偶联。该项目将培训研究生和博士后研究人员，并将他们参与大型国际实验。在与新西兰和日本科学家进行的这项大型合作实验中，将在新西兰北岛东海岸部署两年的海洋底部测量，海洋学和地震学仪器，在部署过程中预计将发生一个或多个浅水区。 关节阵列将包括44个海底绝对压力表（APG）和12个电流米和向上的声纳，以测试和开发创新的方法，以消除水柱内发生的污染压力变化（标记为海洋学噪声）。降低的噪声海底数据将使近海慢滑行事件（SSE）的时空演化更准确地描述。首次将部署11个配备有一个用于从传感器数据中删除长期漂移的系统的APG传感器的阵列，并将在海洋学观测中具有潜在的长期益处，并以构造应变速率应用海底垂直地球地球地球地图。联合阵列中21个海洋底部地震米的数据将用于探测地震与震颤与海底SSE之间的关系。这些观察结果将提高我们对俯冲区域板耦合的近海变化的理解。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准通过评估来支持的。