Collaborative Research: Seismic Investigation of Slab Structure and Back Arc Volcanism in the Sea of Japan Region

合作研究：日本海地区板状构造和弧后火山活动的地震调查

• 批准号: 1547494
• 负责人: Stephen Grand
• 金额: $ 27.18万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-15 至 2019-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1547494&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; Investigation; Slab

We propose to develop a seismic image of the crust and mantle beneath Northeast China, Korea, and Japan with unprecedented resolution. This region is tectonically active and includes a subduction zone beneath Japan that has produced large devastating earthquakes (for example the 2011 Tohoku event), active volcanoes both in Japan as well as in Northeast China, and a history of extension in Northeast China that has resulted in a sedimentary basin rich in natural resources such as coal and oil. Current seismic images of the region will be improved through recent increased data coverage in the region as well as using a new numerical inversion technique that will fit seismic waveforms as well as travel times. The ultimate goal of developing the new seismic models is to better understand the physical processes in the deep Earth in this complicated region and how they relate to the surface tectonic activity.The inversion will utilize 3D spectral element methods to model wave propagation. Adjoint sources will be used in combination with linear optimization methods to invert observed waveforms for seismic velocity. Through waveform inversion we will model triplicated waveforms as well as multipathed seismic arrivals. This type of information has not been used in previous tomographic imaging of the region and thus will result in far higher resolution images than was previously attainable. We will use the crosscorrelation between data and synthetics as an objective function rather than time delays. This is ideal for modeling data that consist of multiple arrivals interfering within short time windows but at the same time it is insensitive to the absolute amplitude of the data. Although this project is essentially seismic in nature, the resulting high resolution images will place constraints on a number of important tectonic processes and questions such as:1. Can all slab subducted beneath Japan for the past 50 Ma be accounted for as seismically fast anomalies?2. Are there stagnant slabs in the deep upper mantle that are detached from the current subducting Pacific plate? If we find segmentation in slabs beneath eastern Asia, can they be associated with the opening of the Japan Sea, as well as Cenozoic magmatism in NE China?3. Is there a warm upwelling coming from beneath stagnant slabs feeding Changbaishan volcano? Are there plumes rising from above the slab feeding volcanic activity in NE China?4. Is there a slab gap associated with the deep seismicity gap beneath the Japan Sea? If so, can this gap be related to the ?hole? observed in the stagnant slabs beneath NE China?5. Can metastable phases be imaged within subducting slab? Can low velocity structures likely associated with water transport into the mantle be imaged?

我们建议以前所未有的分辨率开发中国东北、韩国和日本下方地壳和地幔的地震图像。该地区构造活跃，包括日本下方的俯冲带，该俯冲带曾产生过大型毁灭性地震（例如 2011 年东北地震）、日本和中国东北地区的活火山，以及中国东北地区的扩张历史位于富含煤炭和石油等自然资源的沉积盆地。通过最近增加该地区的数据覆盖范围以及使用适合地震波形和走时的新数值反演技术，该地区当前的地震图像将得到改善。开发新地震模型的最终目标是更好地了解这个复杂区域的地球深处的物理过程以及它们与地表构造活动的关系。反演将利用 3D 谱元方法来模拟波传播。伴随源将与线性优化方法结合使用，以反演观测到的地震速度波形。通过波形反演，我们将对三次波形以及多径地震到达进行建模。这种类型的信息尚未在该区域的先前断层摄影成像中使用，因此将产生比先前可获得的分辨率高得多的图像。 我们将使用数据和合成之间的互相关性作为目标函数，而不是时间延迟。这对于对由短时间窗口内的多个到达干扰组成的数据进行建模是理想的，但同时它对数据的绝对幅度不敏感。尽管该项目本质上是地震项目，但由此产生的高分辨率图像将对许多重要的构造过程和问题产生限制，例如：1。 过去 50 Ma 内俯冲到日本下方的所有板片能否被解释为地震快异常？2。上地幔深处是否存在与当前俯冲的太平洋板块分离的静止板块？如果我们在东亚下方的板片中发现分段，它们是否与日本海的开放以及中国东北新生代的岩浆作用有关？3。是否有温暖的上升流从为长白山火山提供水源的停滞板下方传来？中国东北部的火山活动是否有从板片上方升起的羽流？4。是否存在与日本海下方深层地震活动间隙相关的板块间隙？如果是这样，这个间隙是否与“洞”有关？在中国东北部下方的静止板块中观察到？5。亚稳态相可以在俯冲板片内成像吗？是否可以对可能与水输送到地幔有关的低速结构进行成像？