Alaska Amphibious Community Seismic Experiment

这个创新的，大型的海岸线穿越地震实验调查的过程，治理俯冲，地震和火山活动沿着阿拉斯加半岛。阿拉斯加俯冲系统是世界上研究这些过程的最佳地点之一，因为地震和火山爆发规模大而频繁。在过去的世纪里，它比世界上任何其他俯冲带都产生了更多的8级以上地震，以及数千次小地震，这将使研究能够产生地壳，地幔和火山下面的地球物理"声波图"。地震和火山活动也有很大的系统性变化，人们假设这是受到太平洋构造板块性质的巨大变化的影响，该板块在阿拉斯加下面俯冲。地震和火山爆发对区域人口的安全和福祉有重大影响;火山爆发影响跨太平洋航空旅行和运输，该地区的海啸集中在夏威夷和北美西海岸，因此对大量人口构成危险。我们对这些灾害的理解受到了严重阻碍，因为在产生这些事件的区域缺乏地震仪-因此需要在陆地上，特别是在海上部署地震仪。这是一个社区实验：在完成数据收集后，所有数据将立即提供给更广泛的科学界，以促进发现和创新。了解观测到的地震与相互作用板块的物理性质之间的关系将提高我们在阿拉斯加以及全球类似地质环境中描述地震和火山灾害的能力。这些数据和项目将为下一代地球科学家提供一个丰富的培训基地，涉及广泛的学科，选择阿拉斯加作为GeoPRISMS的主要站点，部署阿拉斯加EarthScope移动式阵列地震台站，以及最近开发的一个大型浅水和深水海底地震仪池，为促进对俯冲带的了解提供了一个独特的机会。该项目为陆上和海上地震活动数据收集和快速向社区发布提供资金。部署将包括75个宽带OBS和30个陆地宽带传感器，在2018 - 19年记录15个月。该阵列覆盖了一个广阔的区域，跨越传入板块，巨型逆冲断层和火山弧到远弧后，并包括科迪亚克/卡特迈地区的密集断面。当与TA集成时，阵列从传入的板块延伸到北极海岸1500公里，沿走向跨越700公里。OBS包括20个用于部署在浅水中的屏蔽传感器。所有浅水和9个深水仪器将包括绝对压力计，以捕捉可能的缓慢滑动事件，而5个OBS和6个陆地站点将包括加速度计，以记录大型当地地震而不削波。阿拉斯加俯冲系统的大部分是由巨型逆冲断层事件主导的，在过去的世纪中，M8事件比任何其他俯冲系统都要多，但有些部分显示出蠕动。它还拥有一个世界级的岩浆弧，展示了一系列系统的化学变化和俯冲板块，展示了水合作用，结构和沉积物厚度的变化。拟议的实验旨在提供一个关键的数据集，解决几个广泛的问题：（1）什么样的地震属性的变化会导致地震耦合的变化，发生大地震和俯冲巨型逆冲断层的地震蠕变？(2)俯冲的上地幔是否水化？是什么控制着水化沿着走向的变化？(3)是什么控制着火山弧壳幔结构、火山成分和弧熔体产生区的几何形状的变化？(4)俯冲带所产生的流动和挥发分释放与大规模板块流动和陆下地幔演化是如何相互作用的？这一社区实验收集的数据将通过IRIS数据管理中心立即提供，使地球物理界能够将其用于研究俯冲过程以及地震和火山灾害的基本问题。实验设计的构建是为了利用阿拉斯加TA的同期部署，以鼓励最大限度地利用这两个数据集。在三次巡航中，研究生和早期到中期职业科学家将被选中加入科学团队，学习OBS数据收集，以鼓励广泛使用来自社区新部门的数据。在第四次巡航期间，一组十名本科生将在为期五天的强化预备短期课程后加入科学团队。来自阿拉斯加大学的另外10名本科生将参加讲习班。为了将这项实验的教育机会扩大到当地社区，将从阿拉斯加或土著学校挑选两名K-12教师参加OBS部署巡航，并利用他们的经验设计课程计划供公众分发。PI团队的10名成员是通过开放申请程序选出的，其中包括多名从这一领导机会中受益的早期职业科学家。

This innovative, large shoreline-crossing seismic experiment investigates the processes that govern subduction, earthquakes, and volcanism along the Alaska Peninsula. The Alaskan subduction system is one of the best places in the world to study these processes, because earthquakes and volcanic eruptions are large and frequent. It has generated more magnitude 8+ earthquakes during the past century than any other subduction zone in the world, as well as thousands of small earthquakes that will allow the research to produce geophysical "sonograms" of the Earth's crust, mantle and beneath its volcanoes. There is also much systematic variability in earthquake and volcano behavior, which has been hypothesized to be influenced by the tremendous variability in the nature of the Pacific tectonic plate which subducts here beneath Alaska. Earthquakes and volcanic eruptions have significant impacts on the security and well-being of regional populations; eruptions impact trans-Pacific air travel and transport, and tsunamis from this region are focused toward Hawaii and the west coast of North America so pose a danger to a large population. Our understanding of these hazards is severely hampered by a lack of seismometers in the region that produces these events -- thus the need to deploy seismometers onland and particularly offshore. This is a community experiment: after completion of the data collection, all data will be made immediately available to the broader scientific community to spur discovery and innovation. Understanding the relationships between the observed earthquakes and the physical properties of interacting plates will enhance our ability to characterize seismic and volcanic hazards in Alaska, as well as globally in similar geologic settings. The data and project will provide a fertile training ground for the next generation of earth scientists in a broad range of disciplines.The selection of Alaska as a GeoPRISMS primary site, deployment of Alaskan EarthScope Transportable Array (TA) seismic stations, and the recent development of a large pool of both shallow and deep-water ocean bottom seismographs (OBSs) provide a unique opportunity to advance understanding of subduction zones. This project funds onshore and offshore seismicity data collection and rapid release to the community. The deployment will include 75  broadband OBSs and 30 land broadband sensors, recording for 15 months in 2018-19. The array covers a broad area that spans the incoming plate, the megathrust and volcanic arc to the distal backarc, and includes a dense transect in the Kodiak/Katmai region. When integrated with the TA, the array extends 1500 km from incoming plate to the Arctic coast and spans 700 km along strike. The OBSs include 20 shielded sensors for deployment in shallow water. All shallow-water and nine deep-water instruments will include absolute pressure gauges to capture possible slow slip events, while five OBSs and six land sites will include accelerometers to record large local earthquakes without clipping.The project is likely to revolutionize our understanding of subduction zones. Much of the Alaskan subduction system is dominated by megathrust events, hosting more M8 events in the past century than any other subduction system, yet some sections show aseismic creep. It also hosts a world-class magmatic arc displaying a range of systematic along-strike variations in chemistry and a subducting plate exhibiting along-strike variations in hydration, structure, and sediment thickness. The proposed experiment is designed to provide a critical data set addressing several broad questions: (1) What changes in seismic properties cause variation in seismic coupling, the occurrence of great earthquakes and aseismic creep on subduction megathrusts? (2) Is the subducting uppermost mantle hydrated and what controls variations in hydration along strike? (3) What controls variations in volcanic arc crust/mantle structure, volcanic composition and the geometry of the arc melt production region? (4) How does the flow and volatile release generated by subduction zones interact with large-scale plate flow and the evolution of sub-continental mantle?Data collected by this community experiment will be made publically available immediately via the IRIS Data Management Center, allowing the geophysical community to use them in research of fundamental questions about subduction processes as well as seismic and volcanic hazards. Experiment design was constructed to leverage contemporaneous deployment of the Alaska TA to encourage maximal use of both datasets. During three cruises, graduate students and early to mid career scientists will be selected to join the science crew, learning about OBS data collection, to encourage the widespread use of the data from new sectors of the community. During the fourth cruise, a group of ten undergraduates will join the science team following a five-day intensive preparatory short course. An additional 10 undergraduate students from Alaskan universities will participate in the workshop. To extend the educational opportunities of this experiment to local communities, two K-12 teachers from Alaskan or Native schools will be selected to participate in OBS deployment cruise and use their experiences to design lesson plans for public distribution. The 10-member PI team was chosen through an open application process and includes multiple early-career scientists benefitting from this leadership opportunity.