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、朝鲜和日本地壳和地幔的地震图像。这一地区构造活跃，包括日本下方的俯冲带，该俯冲带产生了巨大的破坏性地震（例如2011年东北地震），日本和中国东北都有活火山，中国东北的伸展历史导致了富含煤炭和石油等自然资源的沉积盆地。通过最近增加该区域的数据覆盖面，以及使用一种新的数字反演技术，使地震波形和旅行时间相吻合，将改善该区域目前的地震图像。开发新的地震模型的最终目的是更好地了解这一复杂地区地球深部的物理过程及其与地表构造活动的关系，反演将利用三维谱元方法模拟波的传播。伴随源将与线性优化方法结合使用，以反演地震速度的观测波形。通过波形反演，我们将模拟三重波形以及多道地震波至。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，因此将导致比先前可获得的分辨率高得多的分辨率图像。 我们将使用数据和合成之间的互相关作为目标函数，而不是时间延迟。这对于由短时间窗口内的多个波至干扰组成的数据建模是理想的，但同时它对数据的绝对幅度不敏感。虽然这个项目本质上是地震性质的，产生的高分辨率图像将对一些重要的构造过程和问题，如：1。 过去50 Ma所有俯冲到日本下面的板块都能被解释为地震快速异常吗？2.在上地幔深处是否有从俯冲的太平洋板块分离出来的静止板块？如果我们在东亚板块中发现分段现象，它们是否与日本海的打开以及中国东北的新生代岩浆活动有关？3.有没有一股温暖的上升流从长白山火山的停滞板下面涌出来？在中国东北是否有从板块上方升起的羽状物供给火山活动？4.在日本海之下是否存在与深地震空区相关的板块空区？如果是这样的话，这个差距是否与？洞？在中国东北的静止板块中观察到的？5.亚稳相能在俯冲板片中成像吗？可能与水输运到地幔中有关的低速结构能被成像吗？