Collaborative Research: Quantifying the thermal effects of fluid circulation in oceanic crust entering the Cascadia subduction zone

合作研究：量化进入卡斯卡迪亚俯冲带的洋壳中流体循环的热效应

• 批准号: 2034896
• 负责人: Glenn Spinelli
• 金额: $ 39.86万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2034896&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; thermal; effects

Collaborative Research: Quantifying the thermal effects of fluid circulation in oceanic crust entering the Cascadia subduction zoneSubduction zones, where one tectonic plate moves under another, generate the world’s largest earthquakes and tsunamis. Temperatures along the subduction zone fault that separates the two tectonic plates affect friction, thus influencing the size and distribution of earthquakes. In addition, subduction zone temperatures affect a wide range of other physical and chemical processes, including the generation of magma that supplies some volcanoes. To understand these processes, it is important to accurately estimate subduction zone temperatures. Seawater circulating in the subducting tectonic plate can be an important control on subduction zone temperatures. For the Cascadia subduction zone offshore the Pacific Northwest of the United States, the spatial extent and vigor of this seawater circulation is not well known, leading to substantial uncertainty in temperature estimates for this hazardous subduction zone. This study will collect temperature measurements in seafloor sediments offshore Washington and Oregon, and map the distribution of those sediments, to understand the controls on temperatures in the system and improve estimates of subduction zone temperatures. The results of this research have direct societal benefit, by informing earthquake hazard estimates. In addition, the proposed project will enhance education at New Mexico Tech, a STEM-focused Hispanic-serving institution. Two graduate students will be trained in geophysics and hydrogeology. Results of the project will be incorporated into “using data in the classroom” efforts, improving hands-on experience in undergraduate courses.Accurate estimates of subduction zone temperatures are required to understand a variety of critical processes, including controls on seismogenic and aseismic behavior on subduction megathrusts. For the Cascadia subduction zone, the dearth of instrumentally recorded interplate seismicity requires a reliance on indirect methods (including temperature) to estimate the extent of the seismogenic zone. The extent to which fluid circulation redistributes heat within the subducting plate has profound implications for temperature distributions in the Cascadia subduction zone. In Cascadia, a lack of heat flux data immediately seaward of the deformation front is a significant knowledge gap for understanding subduction zone temperatures. This study will fill this hole by collecting ~600 km of seismic reflection lines and ~200 heat flux measurements at 5 sites offshore Washington and Oregon with a focus on quantifying the extent and vigor of hydrothermal circulation in the Juan de Fuca plate. Hydrothermal circulation associated with basement relief generates large anomalies in heat flux across the seafloor; this signal provides a test for the presence of hydrothermal circulation. Combining data from multiple sites will provide information on whether hydrothermal circulation is local or regional. The central hypotheses are: 1) Hydrothermal circulation is ubiquitous in the upper oceanic crustal aquifer; it persists in the aquifer covered by a thick mantle of sediment near the deformation front and in the shallowly subducted crust; and 2) Pseudofaults along propagator wakes are zones of high permeability through the full thickness of the crust; thus, they are zones of enhanced fluid and heat circulation relative to areas outside of propagator wakes. Comparisons of mean heat flux values with those predicted from lithospheric cooling models will allow assessment of whether heat in addition to the basal heat flux is added to the system (e.g., heat transported seaward through the subducting oceanic crust and/or heat advected upwards through faults in propagator wakes). Analyzing and interpreting the controls on the thermal state of the Juan de Fuca plate near the deformation front will allow for the development of improved predictive models of subduction zone temperatures.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.

合作研究：量化海洋地壳中进入卡斯卡迪亚俯冲带的流体循环的热效应俯冲带，一个构造板块在另一个板块下移动，产生世界上最大的地震和海啸。沿着分隔两个构造板块的俯冲带断层的温度影响摩擦力，从而影响地震的规模和分布。此外，俯冲带的温度还影响着其他广泛的物理和化学过程，包括为一些火山提供岩浆的生成。为了理解这些过程，准确估计俯冲带的温度是很重要的。海水在俯冲构造板块中的循环是俯冲带温度的重要控制因素。对于美国太平洋西北部近海的卡斯卡迪亚俯冲带，这种海水循环的空间范围和活力并不为人所知，导致对这一危险俯冲带的温度估计存在很大的不确定性。这项研究将收集华盛顿和俄勒冈州近海海底沉积物的温度测量值，并绘制这些沉积物的分布图，以了解对系统温度的控制，并改进对俯冲带温度的估计。这项研究的结果具有直接的社会效益，通过通知地震灾害估计。此外，拟议的项目将加强新墨西哥州技术，一个以STEM为重点的西班牙裔服务机构的教育。两名研究生将接受地球物理学和水文地质学培训。该项目的结果将被纳入“在课堂上使用数据”的努力，提高实践经验，在本科课程。精确估计俯冲带温度是需要了解各种关键过程，包括控制地震和地震的行为俯冲巨型逆冲断层。对于卡斯卡迪亚俯冲带，缺乏仪器记录的板间地震活动需要依赖间接方法（包括温度）来估计孕震区的范围。流体循环在俯冲板块内重新分配热量的程度对卡斯卡迪亚俯冲带的温度分布有着深远的影响。在卡斯卡迪亚，缺乏热通量数据立即向海的变形锋是一个重大的知识差距，了解俯冲带的温度。这项研究将通过收集华盛顿和俄勒冈州近海5个地点的~600 km地震反射线和~200个热通量测量值来填补这个漏洞，重点是量化胡安德富卡板块热液循环的程度和活力。与基底起伏有关的热液循环在海底的热通量方面产生很大的异常;这一信号为热液循环的存在提供了检验。综合多个地点的数据将提供关于热液循环是局部还是区域性的信息。核心假设是：1）热液循环普遍存在于上大洋地壳含水层中;它持续存在于变形前沿附近被厚沉积物地幔覆盖的含水层和浅俯冲地壳中; 2）沿传播体尾流沿着的假断层是贯穿地壳全厚度的高渗透性区域;因此，相对于传播体尾流以外的区域，它们是流体和热循环增强的区域。将平均热通量值与岩石圈冷却模型预测的热通量值进行比较，将有助于评估除了基底热通量之外，是否还有热量被添加到系统中（例如，通过俯冲洋壳向海洋输送的热量和/或通过传播尾流中的断层向上平流输送的热量）。分析和解释胡安·德富卡板块在变形前沿附近的热状态控制将允许改进俯冲带温度预测模型的发展。该奖项反映了NSF的法定使命，并被认为值得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来支持。

项目成果

Thermally Significant Fluid Seepage Through Thick Sediment on the Juan de Fuca Plate Entering the Cascadia Subduction Zone

进入卡斯卡迪亚俯冲带的胡安德富卡板块上厚沉积物的热显着流体渗漏

• DOI: 10.1029/2023gc010868
• 发表时间: 2023
• 期刊: Geosystems
• 作者: Norvell, Benjamin;Kyritz, Thomas;Spinelli, Glenn A.;Harris, Robert N.;Dickerson, Kristin;Tréhu, Anne M.;Carbotte, Suzanne;Han, Shuoshuo;Boston, Brian;Lee, Michelle
• 通讯作者: Lee, Michelle

Heat flux data from the MARGIN seep site, 2022 (MGL2208)

来自 MARGIN 渗漏点的热通量数据，2022 年 (MGL2208)

• DOI: 10.26022/ieda/331310
• 发表时间: 2023
• 期刊: Interdisciplinary Earth Data Alliance (IEDA
• 作者: Spinelli, Glenn;Harris, Robert;Trehu, Anne
• 通讯作者: Trehu, Anne