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：量化进入卡斯卡迪亚俯冲带的洋壳中流体循环的热效应俯冲带，一个构造板块移动到另一个构造板块下方，产生世界上最大的地震和海啸。分隔两个板块的俯冲带断层沿线的温度会影响摩擦力，从而影响地震的规模和分布。此外，俯冲带温度影响广泛的其他物理和化学过程，包括供应一些火山的岩浆的产生。为了了解这些过程，准确估计俯冲带温度非常重要。俯冲板块中循环的海水可以对俯冲带温度起到重要的控制作用。对于美国西北太平洋近海的卡斯卡迪亚俯冲带，该海水环流的空间范围和强度尚不清楚，导致该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州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，以了解系统中温度的控制并改进对俯冲带温度的估计。这项研究的结果可以为地震灾害估计提供直接的社会效益。此外，拟议的项目将加强新墨西哥理工学院的教育，这是一家专注于 STEM 的西班牙裔服务机构。两名研究生将接受地球物理学和水文地质学方面的培训。该项目的结果将被纳入“在课堂上使用数据”的努力，改善本科课程的实践经验。需要准确估计俯冲带温度以了解各种关键过程，包括对俯冲巨型逆冲断层的发震和抗震行为的控制。对于卡斯卡迪亚俯冲带，由于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）来估计地震发生带的范围。俯冲板块内流体循环重新分配热量的程度对卡斯卡迪亚俯冲带的温度分布具有深远的影响。在卡斯卡迪亚，缺乏紧邻变形前沿的热通量数据是了解俯冲带温度的一个重大知识差距。这项研究将通过在华盛顿州和俄勒冈州近海的 5 个地点收集约 600 公里的地震反射线和约 200 个热通量测量值来填补这一空白，重点是量化胡安德富卡板块热液循环的范围和强度。与基底起伏相关的热液循环会导致海底热通量出现巨大异常；该信号可以测试是否存在热液循环。结合多个地点的数据将提供有关热液循环是局部的还是区域性的信息。中心假设是：1）热液循环在上洋壳含水层中普遍存在；它持续存在于变形前缘附近被厚厚的沉积物覆盖的含水层中以及浅俯冲的地壳中； 2) 沿着传播尾流的假断层是穿过地壳整个厚度的高渗透性区域；因此，相对于传播器尾流之外的区域，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值进行比较，可以评估除了基础热通量之外是否还向系统添加热量（例如，通过俯冲洋壳向海传输的热量和/或通过传播器尾流中的断层向上平流的热量）。分析和解释对变形前缘附近胡安德富卡板块热状态的控制将有助于开发改进的俯冲带温度预测模型。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。

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