Testing contrasting models for the distribution of hydrothermal circulation in subducting crust

俯冲带是地球的一个构造板块移动到另一个板块之下的地方，导致了许多世界上最大的地震和破坏性海啸。一个例子是2011年日本北方的地震和海啸，造成2万多人死亡，福岛第一核电站瘫痪。这些地震是由分隔两个构造板块的俯冲带断层的摩擦引起的。 俯冲断层带的温度影响这种摩擦力，并能控制地震的规模和分布。此外，俯冲带的温度还影响着其他广泛的物理和化学过程，包括为附近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。最近的发现表明，海水在俯冲构造板块内循环是俯冲带温度的重要控制因素。该项目将研究在构造板块上部弯曲进入俯冲带时打开的裂缝如何影响系统中的海水循环，以及如何影响俯冲带温度。该项目将为七个俯冲带建立数值热模型。本研究成果的应用具有直接的社会效益，为地震灾害评估提供了信息。此外，该项目还将加强新墨西哥州理工学院的教育，这是一个以STEM为重点的西班牙裔服务机构。一名研究生将接受地球物理学和水文地质学方面的培训。该项目的成果将被纳入“在课堂上使用数据”的努力，提高实践经验，在本科课程。精确的俯冲带热模型是必要的，以了解摩擦行为，变质反应的进展，从俯冲板，地幔楔水合作用，俯冲动力学和熔体的产生挥发分的释放。大洋地壳含水层中的流体循环是俯冲带温度的重要控制因素。然而，对于有多少海洋地壳可以容纳活跃的热液循环，存在着相反的假设。海洋地壳含水层通过板块弯曲正断层增厚和俯冲地壳与海沟向海地壳之间的流体循环可能有助于影响俯冲带温度的热量平流再分布。本项目将检验一种假设，即俯冲前含水层增厚的热效应对曲率较大的板块更大。该项目将利用以下事实，即从外部隆起到海沟的含水层增厚和俯冲地壳中持续的流体循环预计会产生明显的地表热通量异常（含水层增厚的广泛低幅度异常;俯冲地壳中流体循环的狭窄高幅度异常），以限制每个过程的热效应。这将促进我们对流体循环过程的理解，这是对俯冲带温度的重要控制，改进了本项目和其他项目中检查的七个边缘的俯冲带热模型。

Subduction zones are where one of Earth's tectonic plates moves under another resulting in many of the world's largest earthquakes and damaging tsunamis. One example is the 2011 earthquake and tsunami in northern Japan that killed more than 20,000 people and crippled the Fukushima Daiichi nuclear complex. These earthquakes arise from friction on the subduction zone fault that separates the two tectonic plates. The temperature of the subduction fault zone affects this friction and can control 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 nearby volcanoes. To understand these processes, it is important to accurately estimate subduction zone temperatures. Recent discoveries show that seawater circulating within the subducting tectonic plates is an important control on subduction zone temperatures. This project will examine how fractures that open in the upper part of a tectonic plate as it bends down into a subduction zone affect seawater circulation in the system and how that affects subduction zone temperatures. The project will develop numerical thermal models for seven subduction zones. Application of the results of this research has direct societal benefit, by informing earthquake hazard estimates. In addition, the project will enhance education at New Mexico Tech, a STEM-focused Hispanic-serving institution. A graduate student 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 subduction zone thermal models are necessary to understand frictional behavior, metamorphic reaction progress, release of volatiles from the subducting slab, mantle wedge hydration, subduction dynamics, and melt generation. Fluid circulation in an oceanic crustal aquifer is an important control on subduction zone temperatures. However, there are contrasting hypotheses for how much of the oceanic crust can host vigorous hydrothermal circulation. Both thickening of the oceanic crustal aquifer via plate bending normal faults and fluid circulation between subducted crust and the crust seaward of the trench may contribute to the advective redistribution of heat that affects subduction zone temperatures. This project will test the hypothesis that the thermal effects of aquifer thickening prior to subduction are greater for slabs with a greater degree of curvature. This project will exploit the fact that aquifer thickening from the outer rise to the trench and continued fluid circulation in subducting crust are expected to produce distinct surface heat flux anomalies (a broad low amplitude anomaly for aquifer thickening; a narrow high amplitude anomaly for fluid circulation in subducting crust) in order to constrain the thermal effects of each process. This will advance our understanding of the fluid circulation process that is an important control on subduction zone temperatures, improving subduction zone thermal models for the seven margins examined in this project and others.