Collaborative Research: An Earthscope Magnetotelluric Survey of the Southern Cascadia Subduction System, Washington

合作研究：华盛顿州卡斯卡迪亚南部俯冲系统的 Earthscope 大地电磁勘探

• 批准号: 0843725
• 负责人: Philip Wannamaker
• 金额: $ 37.5万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-15 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0843725&HistoricalAwards=false
• 关键词: Collaborative; Research; Earthscope; Magnetotelluric; Survey

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The Pacific Northwest, and Washington State in particular, are characterized by a subduction zone environment called the Cascadia subduction system. The Cascadia subduction system is an area of the Earth where the seafloor is colliding with, and is being pushed below the overriding crust of the North American continent. The recycling of the seafloor beneath the continent is a complex process: the collision and descent of the seafloor can cause major earthquakes, slow slip and tremor, and volcanic eruptions such as that seen at Mount St Helens and Mount Redoubt. In order to understand these potentially devastating processes, the internal structure of the Earth needs to be imaged at the point where earthquakes, fluid release and melting are triggered, to depths of up to 200 kilometers beneath the surface. Seismic techniques for looking into the Earth's interior are familiar to most people, and they have been used in the Pacific Northwest as part of the USA wide Earthscope program. However, other methods of imaging the Earth, such as the magnetotelluric (MT) method, can provide information regarding the thermal structure of the Earth and can pinpoint areas containing deep released fluids and molten rock. MT uses naturally occurring electric currents generated by lightning activity and by solar wind-ionospheric interactions, to estimate Earth's electrical conductivity. Conductivity in turn depends partly on composition and temperature, but it can be dramatically increased by small amounts of fluid or melt provided that they form an interconnected network. The EarthScope program has also established an array of MT stations over the U.S. Cascadia subduction system, but the existing coverage lacks the spatial resolution to address some of the key issues related to the dynamics of the subduction zone. To rectify this situation, scientists from the University of Utah and Woods Hole Oceanographic Institute are collecting a dense profile of MT stations across west-central Washington State coincident with a previously recorded seismic profile, to rectify this situation. The co-located seismic data will allow the development of techniques for jointly interpreting the two complementary techniques and will provide insights into the understanding of the evolution of the Cascadia subduction system. Societal benefits associated with this research include applications to understanding of processes that contribute to seismic and volcanic hazards associated with the Cascadia subduction system, contributions to research infrastructure, and training of graduate students.

该奖项根据 2009 年美国复苏和再投资法案（公法 111-5）提供资金。太平洋西北地区，尤其是华盛顿州，以称为卡斯卡迪亚俯冲系统的俯冲带环境为特征。卡斯卡迪亚俯冲系统是地球上的一个区域，海底正在与北美大陆的地壳碰撞并被推到地壳以下。大陆下方海底的循环是一个复杂的过程：海底的碰撞和下降可能会引起大地震、缓慢滑动和颤动，以及火山喷发，例如圣海伦斯火山和堡垒山的火山喷发。为了了解这些潜在的破坏性过程，需要对地震、流体释放和融化触发点（地表以下 200 公里的深度）的地球内部结构进行成像。大多数人都熟悉用于观察地球内部的地震技术，并且作为美国地球范围计划的一部分，这些技术已在太平洋西北地区使用。然而，其他地球成像方法，例如大地电磁 (MT) 方法，可以提供有关地球热结构的信息，并可以查明含有深层释放流体和熔岩的区域。 MT 利用闪电活动和太阳风与电离层相互作用产生的自然电流来估计地球的电导率。电导率又部分取决于成分和温度，但只要少量流体或熔体形成互连网络，电导率就可以显着提高。 EarthScope 计划还在美国卡斯卡迪亚俯冲系统上建立了一系列 MT 站，但现有的覆盖范围缺乏空间分辨率，无法解决与俯冲带动态相关的一些关键问题。为了纠正这种情况，犹他大学和伍兹霍尔海洋研究所的科学家正在收集华盛顿州中西部地区与先前记录的地震剖面相一致的密集MT站剖面，以纠正这种情况。同一地点的地震数据将有助于开发联合解释这两种互补技术的技术，并将为理解卡斯卡迪亚俯冲系统的演化提供见解。与这项研究相关的社会效益包括应用于理解与卡斯卡迪亚俯冲系统相关的地震和火山灾害的过程、对研究基础设施的贡献以及研究生的培训。