The Mechanics of Subduction in Japan from High-Precision Earthquake Location and Tomography

从高精度地震定位和断层扫描研究日本俯冲机制

• 批准号: 0409917
• 负责人: Gregory Beroza
• 金额: $ 25.79万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409917&HistoricalAwards=false
• 关键词: Mechanics; Subduction; Japan; Precision; Earthquake

THE MECHANICS OF SUBDUCTION IN JAPAN FROM HIGH-PRECISION EARTHQUAKE LOCATION AND TOMOGRAPHYP.I. Gregory C. BerozaSubduction zone plate boundaries are host the largest known earthquakes. They are also the sites of damaging upper crustal and intermediate-depth earthquakes that in themselves pose substantial seismic hazard. Under this grant we are developing an improved understanding of the mechanics of shallow and intermediate-depth earthquakes in the subduction zone in Japan. Japan is the ideal place for our study for several reasons. Subduction zones in Japan exhibit a diversity of styles including: rapid subduction of old oceanic crust in Hokkaido and North Honshu, nearly flat subduction of much younger Philippine Sea plate in South Honshu and Shikoku, and much steeper subduction of relatively young oceanic crust under the southern island of Kyushu. Japan is highly seismic. Since 1994 there have been over half a million earthquakes recorded by seismic networks in Japan that appear in the JMA catalog. What really sets the subduction zones in Japan apart from those elsewhere on Earth is the level of seismic instrumentation. With over 1500 high-gain short period instruments available for earthquake monitoring, the subduction zones in Japan are by far the best instrumented in the world. Moreover, the new Hi-Net seismic network, which now numbers nearly 700 3-component borehole stations, offers a unique capability for earthquake monitoring found nowhere else. In our research we are applying and improving recently developed high-precision, multiple-event earthquake relocation and high-precision tomography techniques to earthquakes in Japan. These methods have revealed remarkable details of the faulting process in other seismically active regions of the world that have lead to new insights into how earthquakes work and their application to Japan holds similar promise.Our research has two main goals. First are trying to understand the geometry and mechanics of the plate-boundary interface, where the very largest earthquakes occur, and the factors that limit the depth extent of their occurrence. The combination of precise earthquake locations and how they are situated relative to the velocity structure at depth is the key to this analysis. Second, we are trying to relate precisely located earthquakes to the detailed seismic velocity structure of the downgoing plate. We are particularly interested in constraining the possible role that dehydration reactions due to metamorphism in the downgoing plate play in enabling intermediate-depth earthquakes.

日本高精度地震位置和层表型的俯冲机制。 Gregory C. Berozasubduction区板边界是最大的已知地震。 它们也是破坏上层地壳和中间严重地震的地点，这些地震本身构成了巨大的地震危险。 根据这笔赠款，我们正在对日本俯冲带的浅层和中间地震的机制有了改进的了解。 由于几个原因，日本是我们研究的理想场所。日本的俯冲带表现出各种各样的风格，包括：北海道和北洪的旧海壳的快速俯冲，几乎平坦的俯冲俯冲在南洪斯胡（South Honshu）和Shikoku的年轻菲律宾海板和Shikoku，以及在Kyushu Southern Southern Island Kyushu岛下相对年轻的海洋甲壳的俯冲。 日本高度地震。 自1994年以来，日本地震网络记录了超过半百万的地震，出现在JMA目录中。 真正使日本俯冲带与地球其他地方不同的是地震仪器的水平。 有1500多个高级短期仪器可用于地震监测，日本的俯冲带是迄今为止世界上最好的仪器。 此外，现在的新型Hi-NET地震网络现在编号近700个3组分钻孔站，为地震监测提供了独特的功能。 在我们的研究中，我们将最近开发的高精度，多事件地震搬迁和高精度断层扫描技术应用于日本的地震。 这些方法揭示了世界上其他具有地震活跃地区的断层过程的显着细节，这使人们对地震的运作方式及其在日本的应用具有新的见解。我们的研究具有两个主要目标。 首先是试图了解最大地震发生的板界界面的几何形状和力学，以及限制其发生深度范围的因素。 精确的地震位置及其相对于深度速度结构的位置的结合是该分析的关键。 其次，我们试图将精确的地震与下板的详细地震速度结构联系起来。 我们特别有兴趣限制在下层板在实现中间深度地震中由于变质引起的脱水反应的可能作用。