| 项目编号: | 1735960
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| 项目名称: | Near-Surface Structure of the Continental United States Using Distant Earthquakes |
| 作者: | Miaki Ishii
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| 承担单位: | Harvard University
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| 批准年: | 2017
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| 开始日期: | 2017-09-01
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| 结束日期: | 2018-08-31
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| 资助金额: | 63889
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Earth Sciences
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| 英文关键词: | near-surface
; surface
; continental united states
; wave speed
; seismic structure
; near-surface critical zone study
; united states
; near-surface structure
; earthquake early warning
; shallow subsurface
; distant earthquake datum
; earthquake engineering
; soil/crust structure
; subsurface imaging
|
| 英文摘要: | This project examines shallowest structure of the United States using a novel approach that utilizes EarthScope USArray seismic data. Depth-dependent estimates of both compressional- and shear-wave speeds will contribute not only to the studies of the subsurface imaging, but also to seismic hazard assessment and earthquake engineering. The new method is non-invasive, such that well drilling or field experiments using explosives are not necessary, and can be applied to any site with a single seismic station or dense arrays. Furthermore, if depth dependence is not sought, easy-to-install and inexpensive instruments can be used, allowing detailed variations
in the soil/crust structure to be revealed at low cost. The near-surface structure obtained from this study can be used as an input model for ground motion simulations, and will contribute to such programs as earthquake early warning that requires shaking predictions at critical locations. This project will also promote multidisciplinary research on the geological study of the continental United States. Since the technique can resolve seismic structure of top few kilometers or less, the lateral variation revealed from this study can be compared to and interpreted with geological provinces observed at the surface. The shallowness of the target also starts to bring together the global seismological analysis (using distant earthquake data) with near-surface critical zone studies, and contribute to our understanding of complex processes that occur at the Earth's surface.
The new technique utilizes body-wave polarization to resolve wave speed immediately beneath a seismic station. Seismic wave polarization information has been relatively unexploited compared to other quantities such as travel times, and the essential theoretical framework for relating the polarization information of teleseismic body waves to near-surface wave speeds will be established and tested. Counter-intuitively, the polarization of teleseismic P waves is sensitive to shear-wave speed, while that of S waves is sensitive to both compressional and shear-wave speeds. Moreover, examining the frequency dependence of the polarization data allows a depth-dependent wave speed model of the shallow subsurface to be constructed. The method will be applied to the USArray data to produce the near-surface wave speed model of the continental United States. The spatial variation of the wave speeds, in both vertical and horizontal dimensions, will be studied at different scales through different frequency filters and combination of data from Transportable Array, Reference Network, and Flexible Array. The results will provide better constraints on the crust properties, and can be used to improve crustal corrections used for other types of studies such as global or regional seismic tomography. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/89177
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Miaki Ishii. Near-Surface Structure of the Continental United States Using Distant Earthquakes. 2017-01-01.
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