EAGER: Bubble Plume Emissions from Fault Zones within the Puget Sound Forearc

EAGER：普吉特湾前弧内断层带的气泡羽流排放

• 批准号: 1945975
• 负责人: Harlan Johnson
• 金额: $ 9.4万
• 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: 2019-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1945975&HistoricalAwards=false
• 关键词: EAGER; Bubble; Plume; Emissions; Fault

This EAGER proposal will obtain samples from newly identified gas and fluid plumes in Puget Sound to determine whether the plumes come from the Cascadia subduction zone megathrust. The idea is that deep regional faults act as pathways for upward migration of fluid that has been generated by heating along the plate interface between the North America and the incoming Juan de Fuca Plate. If the Puget Sound plumes have a subduction zone source, the plumes may provide a means to monitor the pressure and chemistry of the fluid between the plates, and provide a new approach for studying slip on the Cascadia subduction zone megathrust fault. This project is a first step toward developing predictive models for understanding seismic hazards in the heavily-populated Pacific Northwest.Upward migration of fluid and gas through the forearc crust that overlies active subduction zone faults has been observed in settings very similar to the Puget Sound region, including Japan Trench on the Kii peninsula, New Zealand at the Hikurangi margin, and on the Baja California Peninsula, Mexico. Although these fluid seeps emit fluid with helium, oxygen, hydrogen isotope signatures that unambiguously identify them as coming from the subduction zone fault, none of them emit fluid and gas with the vigor or wide spatial distribution observed within Puget Sound. Critically, none of the previous globally-identified forearc plumes are in subduction zones where periodic Episodic Tremor and Slip (ETS) events occur - that arise from periodic local slippage on the subduction zone fault. At Cascadia, these ETS events have a quasi-period of 14 months and variations in the amplitude and intervals are newly-recognized as potential precursors to both regional faulting and large episodic megathrust earthquakes. If the the new Puget plumes are found to be derived from the subduction zone megathrust zone, it would be the first step in using correlations between the variations in emissions and ETS behavior to understand slip on the megathrust.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.

这项 EAGER 提案将从普吉特湾新发现的气体和流体羽流中获取样本，以确定这些羽流是否来自卡斯卡迪亚俯冲带巨型逆冲断层。这个想法是，深层区域断层充当流体向上迁移的通道，这些流体是通过沿着北美和即将到来的胡安德富卡板块之间的板块界面加热而产生的。如果普吉特湾羽流有俯冲带源，则羽流可能提供一种监测板块之间流体压力和化学成分的方法，并为研究卡斯卡迪亚俯冲带巨型逆冲断层上的滑移提供新方法。该项目是开发预测模型以了解人口稠密的太平洋西北地区地震灾害的第一步。在与普吉特海湾地区非常相似的环境中观察到流体和气体通过活动俯冲带断层上的弧前地壳向上迁移，包括基伊半岛的日本海沟、新西兰希库朗伊边缘和下加利福尼亚半岛。 墨西哥。尽管这些流体渗漏喷出的流体带有氦、氧、氢同位素特征，可以明确地识别出它们来自俯冲带断层，但它们中没有一个喷出的流体和气体具有在普吉特湾观察到的活力或广泛的空间分布。重要的是，之前全球确认的弧前羽流均不位于发生周期性震颤和滑动（ETS）事件的俯冲带，这些事件是由俯冲带断层上的周期性局部滑动引起的。在卡斯卡迪亚，这些 ETS 事件的准周期为 14 个月，并且振幅和间隔的变化被重新认识为区域断层和大型幕式巨型逆冲地震的潜在前兆。如果发现新的普吉特羽流源自俯冲带巨型逆冲断层带，那么这将是利用排放变化与 ETS 行为之间的相关性来了解巨型逆冲断层滑移的第一步。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。