Collaborative research: Quantifying incoming plate hydration and role of fluids on megathrust properties in and around the Guerrero Gap, offshore Mexico

合作研究：量化进入的板块水合作用以及流体对墨西哥近海格雷罗峡及其周围巨型逆冲断层特性的作用

• 批准号: 2016057
• 负责人: Donna Shillington
• 金额: $ 12.98万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2016057&HistoricalAwards=false
• 关键词: Collaborative; research; Quantifying; incoming; plate

The plate boundary in subduction zone settings is known to exhibit a wide spectrum of behavior for how the two tectonic plates slide past each other. Many questions remain about what controls the wide spectrum of slip behavior within and between different subduction zone systems worldwide. Seawater delivered into the subduction zone by the incoming oceanic plate is commonly invoked to explain variability of plate interface slip behavior. However, the volume and distribution of seawater incorporated into the downgoing oceanic plate and its fate at depth vary between subduction zones and is poorly known owing to the limited amount of existing observations. The Guerrero Gap and neighboring segments at the Middle America subduction zone, offshore Mexico, is one of the best-known examples in the world of along-strike variations in slip behavior of the plate boundary. The Guerrero Gap has not ruptured in a M7 earthquake in more than 100 years but the largest known relatively shallow slow-slip events that release energy slowly without generating strong seismic waves occur approximately every 4 yrs. In contrast, the neighboring segments have ruptured in M7 earthquakes and appear to be strongly locked. This project will involve the acquisition and analysis of marine, active-source seismic data within the Guerrero Seismic Gap and neighboring segments in order to obtain critical constraints on the properties and geometry of the subduction zone faults, including the abundance and distribution of fluids in both the incoming oceanic plate and within the subduction zone. Results from this project will be valuable for understanding the role of fluids (e.g. seawater) in influencing the contrasting slip behavior both at this margin and similar subduction zones. This project will support two early career scientists and one pre-tenured scientist and will involve a strong collaboration between US, Mexican and Japanese scientists. The proposed study will also strongly complement an ongoing amphibious geodetic and seismic deployment led by Mexican and Japanese collaborators. A 47.5 day, combined 2D wide-angle seismic reflection/refraction and ultra-long offset multi-channel seismic (MCS) survey will be conducted onboard the R/V Marcus G. Langseth. This project includes six primary profiles along which both MCS and Ocean Bottom Seismometer (OBS) data will be acquired, and additional MCS profiles that extend seismic imaging over a larger extent of the margin. This study of the Guerrero Gap and neighboring segments will yield unique insights into two core questions: (1) What is the hydration state of the incoming, young sediment-starved Cocos oceanic plate at the Middle America subduction zone, and how does it vary along-strike and relate to changes in subduction zone behavior? MCS imaging and P and S- waves velocity models from OBS and streamer data, including full-waveform inversion as well as joint inversion of shots and earthquakes, will provide the first estimates of the amount and distribution of water in the incoming plate prior to subduction from the ridge axis to the trench axis and both in and outside of the Guerrero Gap, allowing us to examine the role of fluids in subduction zone processes and results will be compared the young but well-sedimented Cascadia and Nankai subducting plates, (2) How do geometrical and material properties of the subducting and overriding plates influence slip behavior along the megathrust fault? Controlled- source seismic data will bring new, high-resolution constraints on the architecture and properties of the upper 20-30 km of this subduction zone on parts of the megathrust that have different degrees of coupling and slip behavior. This will enable the testing of competing ideas for controls on slip behavior developed at other subduction zones, such as variations in pore-fluid pressure or fault zone heterogeneity. Addressing this question will require a synthesis of constraints on plate boundary properties from this project with results on slip behavior from an ongoing multi-year deployment of geodetic and seismic stations within the Guerrero Gap.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.

已知俯冲区设置中的板边界可以表现出两种构造板如何相互滑动的广泛行为。关于控制全球不同俯冲区域内部和不同俯冲区域之间的广泛滑移行为的许多问题。通常调用通过进入的海洋板传递到俯冲带的海水，以解释板界面滑动行为的变异性。但是，掺入到下游的海洋板中的海水的体积和分布及其在俯冲带之间的命运因俯冲带的各不相同，并且由于现有观测量有限，因此众所周知。墨西哥近海的中美洲俯冲带的Guerrero Gap和相邻段是世界上最著名的例子之一。在100多年来，Guerrero Gap并未在M7地震中破裂，但是最大的已知相对较浅的慢滑事事件缓慢地释放了能量，而不会产生强烈的地震波，大约每4年就会发生强烈的地震波。相比之下，附近的细分市场在M7地震中破裂，似乎被强锁定。该项目将涉及对Guerrero地震间隙和邻近细分市场内海洋，主动源地震数据的获取和分析，以便获得对俯冲区故障的性质和几何形状的关键限制，包括在输入的大洋板和俯冲区内流体的丰度和流体分布。该项目的结果对于理解流体（例如海水）在影响此边缘和类似俯冲区域的对比度滑移行为中的作用将是有价值的。该项目将支持两位早期的职业科学家和一名预先陈述的科学家，并将涉及我们，墨西哥和日本科学家之间的强有力合作。拟议的研究还将强烈补充由墨西哥和日本合作者领导的持续的两栖大地测量和地震部署。将在R/V Marcus G. Langseth上进行47.5天的合并2D广角地震反射/倒数和超长偏移多通道地震（MCS）调查。该项目包括六个主要轮廓，将沿着MC和海洋底部地震计（OBS）数据获取，以及在更大范围内扩展地震成像的其他MCS轮廓。这项对Guerrero Gap和相邻段的研究将对两个核心问题产生独特的见解：（1）中美洲俯冲带的传入，年轻沉积物饥饿的可可海板的水合状态是什么，以及它随着撞击的变化以及对俯冲带行为的变化如何变化？ MCS成像以及P和S波从观察和流媒体数据中的速度模型，包括全波倒置以及镜头和地震的联合反转，将提供第一个估计的估计值，以在从山脊轴上俯冲到to to and to to the Guerrero的行为，以相比，从山脊轴进行俯冲之前，我们的脱落和范围的结果是，我们的作用是在Guererre距离之外，以使我们的脱落量相比，我们的作用是在Guirer中进行的。年轻但经过精心挑选的卡斯卡迪亚和南卡俯冲板，（2）（2）俯冲和压倒板的几何和物质特性如何影响沿Megathrust断层的滑移行为？受控的源地震数据将对该俯冲带上层20-30 km的架构和性质产生新的高分辨率约束，并在具有不同程度的耦合和滑动行为的大型象征。这将使对在其他俯冲区域开发的滑移行为的控制进行竞争的想法，例如孔隙流体压力或断层区异质性的变化。解决这个问题将需要综合该项目的板边界属性的约束，并从Guerrero Gap中进行的多年部署进行多年部署，从而取得了滑移行为的结果。这项奖项反映了NSF的法定任务，并通过使用该基金会的知识分子优点和广泛的影响来评估NSF的法定任务，并被视为值得进行的支持。