Near-Surface Structure of the Continental United States Using Distant Earthquakes

GSTDTAP

项目编号	1735960
	Near-Surface Structure of the Continental United States Using Distant Earthquakes
	Miaki Ishii
主持机构	Harvard University
项目开始年	2017
	2017-09-01
项目结束日期	2018-08-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	63889(USD)
国家	美国
语种	英语
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.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/71650
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Miaki Ishii.Near-Surface Structure of the Continental United States Using Distant Earthquakes.2017.