Collaborative Research: Unraveling the habitat and dynamics of slow slip events through integrated borehole observations in the northern Hikurangi subduction margin

合作研究：通过希库朗伊俯冲边缘北部的综合钻孔观测揭示慢滑事件的栖息地和动态

• 批准号: 2132610
• 负责人: Evan Solomon
• 金额: $ 55.13万
• 依托单位: University of Washington
• 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: 2022-02-15 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2132610&HistoricalAwards=false
• 关键词: Collaborative; Research; Unraveling; habitat; dynamics

Subduction zone plate boundaries, where one tectonic plate dives or subducts beneath another tectonic plate produce the world’s largest earthquakes and tsunami, as starkly demonstrated by the M9.2 Indian Ocean earthquake in 2004, and the 2011 M9.0 Tohoku-Oki earthquake offshore northern Japan. Recently, scientists have recognized that subduction megathrust faults undergo slip in episodic slow-motion earthquakes, or slow slip events lasting days to months. In some cases, slow slip events have been observed to precede (and possibly trigger) major subduction earthquakes, increasing the need to understand them. Slow slip events occurring close to Earth's surface (5-15 km depth) exist at the Hikurangi subduction zone offshore New Zealand and are uniquely accessible to near-source investigations. In 2018, two observatories (penetrating up to 400 m below the seafloor) were installed during an International Ocean Discovery Program scientific drilling expedition at the Hikurangi subduction zone. Sensors in the observatories are now continuously measuring temporal changes in properties of Earth's crust near the source of slow slip events and will help reveal their causes, consequences, and relationship to destructive earthquakes. This project provides funding to analyze the data collected from the observatories, and to support another mission to the observatories to retrieve and replace the instrument strings at the observatories to enable their continued operation for another five years. The project supports the training of graduate and undergraduate students.Slow slip events (SSEs) involve transient aseismic slip on a fault (lasting weeks to months) at sliding velocities intermediate between plate boundary displacement rates and those required to generate seismic waves. The physical mechanisms leading to SSEs, their role in plate boundary strain accumulation and release, and their relationship to destructive seismic slip on subduction thrusts are poorly known, due in part to the fact that most well-studied subduction zone SSEs occur far too deep for near-field investigations. A notable exception to this is the northern Hikurangi subduction zone, New Zealand, where well-characterized SSEs occur within 5-15 km below the seafloor, and possibly propagate to the trench. In early 2018, as part of IODP Expedition 375, two borehole observatories were installed in the near field of northern Hikurangi SSEs to monitor deformation, thermal, hydrological, and geochemical responses through multiple SSE cycles. This project will: (1) recover and conduct analyses of data and samples recovered from the observatories; and (2) replace the geochemical sampling and temperature sensing instrument string in one of these boreholes, spanning an active thrust near the deformation front, during a proposed research cruise in early 2023. These data will be integrated with a network of seafloor sensors (absolute pressure gauges, seismometers, and fluid flowmeters) that were also recording along the drilling transect during a large slow slip event in 2019, offering an unprecedented opportunity to integrate multiple seafloor and subseafloor observations in the near-field of a large slow slip event.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.

俯冲带板板边界，其中一个构造板潜水或在另一个构造板下面的横潜能或俯冲板产生了世界上最大的地震和海啸，正如2004年M9.2印度洋地震以及2011年M9.0 Toohoku-Oki地震地震北部日本北部的2011 M9.0 M9.0 Toohoku-Oki地震。最近，科学家已经认识到，俯冲巨型断层在慢速运动慢速地震或持续几天到几个月的慢速事件中遭受滑倒。在某些情况下，已经观察到慢速事件是在（可能触发的）主要俯冲地震之前（可能是触发），从而增加了理解它们的需求。新西兰海上俯冲带的慢速事件存在于地球表面附近的（5-15公里深度），并且可用于近源研究。 2018年，在Hikurangi俯冲带科学钻探探险队的国际海洋发现计划中安装了两名观察员（在海底下方400 m的穿透者）。现在，观察结果中的传感器正在不断测量慢速事件来源附近地壳性质的暂时变化，并将有助于揭示其原因，后果和与破坏性地震的关系。该项目提供了资金来分析从观察结果中收集的数据，并支持在观测值中检索和替换仪器字符串的另一个任务，以使其继续运行五年。该项目支持研究生和本科生的培训。SLOW滑移事件（SSE）涉及在板块边界置换率和产生地震波所需的滑动速度上的断层（持续数周到几个月）上的短暂性无性滑移。导致SSE的物理机制，它们在板边界应变积聚和释放中的作用以及它们与俯冲推力上的破坏性地震滑移的关系是众所周知的，部分原因是最深入的俯冲带的发生得太深了，无法实现近场研究。一个值得注意的例外是新西兰的北部山川俯冲带，在该区域，特征良好的SSE出现在海底下方5-15公里以内，并可能传播到沟槽。在2018年初，作为IODP Expedition 375的一部分，在Hikurangi SSE的近场中安装了两个钻孔观测，以监测通过多个SSE周期的变形，热，水力学和地球化学响应。该项目将：（1）恢复并进行从观测值中恢复的数据和样本的分析； （2）在2023年初的一项拟议的研究巡航期间，在这些钻孔之一中替换了这些钻孔中的一个地球化学采样和温度传感仪器串，跨越了变形前方附近的主动推力。这些数据将与海底传感器网络集成（绝对压力仪表，静电仪，以及在沿钻孔的绝对压力范围内），该网络沿着2019年的巨大距离进行了划线，该沿钻机沿着2019前所未有的机会，将多个海底和亚地下观察结果整合在大型慢速事件的近场中。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准的评估来通过评估来支持的。