Research Infrastructure: Mid-scale RI-1 (M1:IP): Creating an Offshore Subduction Zone Observatory in Cascadia with the Ocean Observatories Initiative Regional Cabled Array

地球上最大的地质灾害集中在俯冲带，也就是两个构造板块汇合和碰撞的地方。所有已知的≥8.8级地震都发生在俯冲带，最具破坏性的海啸也是如此。卡斯卡迪亚俯冲带横跨从加利福尼亚州北部到不列颠哥伦比亚省的近海海岸，每几百年就会发生一次9级地震，上一次是在1700年。尽管今天太平洋西北部的陆地上有密集的地震和大地测量传感器网络，但在美国水域，几乎所有锁定的板块边界和预期的地震滑动都将发生在近海地区，基本上没有这样的仪器。该项目将利用现有的由美国国家科学基金会资助的区域电缆观测站，该观测站将电力和互联网引入俄勒冈州纽波特近海边缘的海洋。包括地震传感器和海底压力计在内的仪器将被添加到电缆基础设施中。来自俯冲带观测站的实时数据将有助于回答有关俯冲带断层如何工作的基本问题，并可用于增强现有的地震和海啸预警系统。当今地球科学中的一个根本的“重大挑战”是提高对俯冲带板块界面断层如何工作的理解。这需要在多个俯冲带进行持续的海上观测，这些观测具有不同的性质，以表征大地震、慢滑和无震蠕变之间的变形划分。卡斯卡迪亚俯冲带是一个全球末端成员，这是因为俯冲板块年龄较小，沉积盖层较厚。海洋观测站倡议区域电缆阵列包括一条位于俄勒冈州纽波特附近卡斯卡迪亚俯冲带斜坡和陆架上的南部电缆。该阵列具有研究俯冲带的巨大潜力，因为它位于卡斯卡迪亚的理想中心位置，在那里，巨型逆冲耦合的梯度延伸到近海，而且陆架下有持续的地震活动和低频地震集群。该项目将在陆坡和陆架上的三个主要节点的每个节点上增加电缆海底科学接线盒，目前这些节点都没有用于地球物理的仪器。每个接线盒将容纳一套地球物理传感器，包括埋置的宽带地震仪、低频水听器、强震加速度计、校准压力计和海流计，并有未来扩展的空间。与已经安装了地球物理传感器的节点相结合，这将创建一个世界级的近海地球物理观测站，以研究卡斯卡迪亚巨型逆冲和上复吸积棱柱在近海约100公里范围内的断层耦合和变形。天文台可以解决以下问题：(1)卡斯卡迪亚巨型逆冲在俄勒冈州中部变形前锋和海岸线之间的锁定是如何过渡的？(2)近海是否存在瞬时滑动行为--慢滑、震颤和/或极低频率地震--横跨锁定带及其向下的过渡？(3)近海浅层地震群如何与巨型逆冲联系在一起？(4)增量棱镜的基线形变率和断层滑动行为是什么？由于海底电缆以光速将数据传输到岸上，该天文台可以提供美国第一个近海实时地震和海啸预警探测器，补充和补充美国地质调查局的ShakeAlert地震预警系统和NOAA的海啸浮标。它还可以支持对新预警技术的研究。本科生暑期实习生和研究生都将接受关于有线地球物理观测站的培训，包括在安装观测站之前和期间的海上体验学习方案。研讨会将向早期职业研究人员介绍科学目标和基础设施，提供访问和可视化数据流的工具的实践经验，并探索未来分析的想法。由于海底电缆以光速将数据传输到海岸，该天文台可以提供美国第一个近海实时地震和海啸预警探测器，对美国地质调查局的ShakeAlert地震预警系统和NOAA的海啸浮标进行补充和补充。它还可以支持对新预警技术的研究。本科生暑期实习生和研究生都将接受关于有线地球物理观测站的培训，包括在安装观测站之前和期间的海上体验学习方案。研讨会将向早期职业研究人员介绍科学目标和基础设施，提供访问和可视化数据流的工具的实践经验，并探索未来分析的想法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Earth’s greatest geological hazards are concentrated in its subduction zones, the places where two tectonic plates converge and collide. All known earthquakes with magnitudes ≥8.8 have taken place at subduction zones, as have the most devastating tsunamis. The Cascadia subduction zone, spanning the offshore coasts from northern California to British Columbia, hosts earthquakes up to magnitude 9 every few hundred years, the last of which was in 1700. While there are dense seismic and geodetic sensor networks today on land in the Pacific Northwest, the offshore region, where almost all the locked plate boundary and expected earthquake slip will occur, is largely devoid of such instruments in US waters. This project will take advantage of the existing NSF-funded Regional Cabled Observatory that brings power and the internet into the oceans on the margin offshore Newport, Oregon. Instruments, including seismic sensors and seafloor pressure gauges, will be added to the cabled infrastructure. Real-time data streaming from the resulting subduction zone observatory will help answer fundamental questions about how subduction zone faults work and can be used to enhance existing systems for earthquake and tsunami warning. A fundamental “Grand Challenge” in the geosciences today is to improve understanding of how subduction zone plate interface faults work. This requires sustained offshore observations in multiple subduction zones with contrasting properties to characterize how deformation is partitioned among large earthquakes, slow slip, and aseismic creep. The Cascadia subduction zone is a global endmember, owing to the young age of the subducting plate and thick sediment cover. The Ocean Observatories Initiative Regional Cabled Array includes a southern cable located on the slope and shelf of the Cascadia subduction zone off Newport, Oregon. This array has great potential for subduction zone studies because it is in an ideal central location in Cascadia where the gradient in megathrust coupling extends well offshore and there are ongoing clusters of seismicity and low frequency earthquakes beneath the shelf. This project will add cabled seafloor science junction boxes to each of three Primary Nodes on the continental slope and shelf, none of which are presently instrumented for geophysics. Each junction box will host a suite of geophysical sensors, comprising a buried broadband seismometer, a low-frequency hydrophone, strong motion accelerometers, calibrated pressure gauges and a current meter, with room for future expansion. In conjunction with nodes that already have geophysical sensors, this will create a world class offshore geophysical observatory to study fault coupling and deformation of the Cascadia megathrust and the overlying accretionary prism across a ~100 km section offshore. The observatory can address the following questions: (1) How does the locking of the Cascadia megathrust transition between the deformation front and the coastline off central Oregon?(2) Is there transient slip behavior – slow slip, tremor, and/or very low frequency earthquakes – offshore spanning the locked zone and its downdip transition? (3) How are the clusters of shallow earthquakes offshore linked to the megathrust?(4) What is the baseline deformation rate and fault slip behavior of the accretionary prism? Because the submarine cable streams data to shore at the speed of light, this observatory can provide the nation’s first offshore real-time earthquake and tsunami early warning detector, adding to and complementing the USGS’s ShakeAlert earthquake warning system and NOAA’s tsunami buoys. It can also support research into new warning technologies. Both undergraduate summer interns and graduate students will be trained on cabled geophysical observatories, including at-sea experiential learning programs prior to and during installation of the observatory. A workshop will introduce early career researchers to the scientific goals and infrastructure, provide hands-on experience with the tools for accessing and visualizing the data streams, and explore ideas for future analysis.Because the submarine cable streams data to shore at the speed of light, this observatory can provide the nation’s first offshore real-time earthquake and tsunami early warning detector, adding to and complementing the USGS’s ShakeAlert earthquake warning system and NOAA’s tsunami buoys. It can also support research into new warning technologies. Both undergraduate summer interns and graduate students will be trained on cabled geophysical observatories, including at-sea experiential learning programs prior to and during installation of the observatory. A workshop will introduce early career researchers to the scientific goals and infrastructure, provide hands-on experience with the tools for accessing and visualizing the data streams, and explore ideas for future analysis.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.