Mapping Small-scale Mantle Heterogeneities Using USArray

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项目编号	1610612
	Mapping Small-scale Mantle Heterogeneities Using USArray
	Jun Korenaga
主持机构	Yale University
项目开始年	2016
	2016-06-01
项目结束日期	2018-05-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	259869(USD)
国家	美国
语种	英语
英文摘要	Mapping small-scale mantle heterogeneities using USArray Deep currents within the rocky portion of the Earth?s interior are called mantle convection, and this is the engine for almost all kinds of geological processes on the Earth, not only generating earthquakes, volcanoes, and continental drift, but also modulating the evolution of the geomagnetic field and even the atmospheric composition. At the same time, understanding how this mantle convection is actually operating is difficult and subject to large uncertainty, because it is mostly hidden from our eyes, except for its surface manifestation known as plate tectonics. One of the fundamental questions regarding mantle convection is how efficiently it can mix things up, and the efficiency of convective mixing has a number of important bearings on how mantle convection has shaped the history of the Earth and its surface environment. In this project, we will apply a state-of-the-art seismic imaging technique to the USArray data, to detect small-scale heterogeneities in the mantle surrounding the North American continent. The distribution of small-scale heterogeneities, when interpreted in the context of the tectonic history of a relevant mantle section, has a potential to elucidate the long-term mixing efficiency of mantle convection. In the last few years, the PI has been developing new data processing tools to overcome various difficulties associated with the detection of small-scale mantle heterogeneities, including a powerful signal detection technique called dual bootstrap stacking (DBS) and a teleseismic migration method based on DBS. Seismic migration is an imaging technique in which seismic energy recorded at surface receivers is projected back to its origin in the subsurface. As it directly uses the entire waveform of seismic data, migration has a potential to achieve the highest spatial resolution allowed by the given data. The Transportable Array of USArray finished its eastward migration in 2013, and the time is ripe to explore the vast wealth of USArray data by DBS-based teleseismic migration in a systematic manner. Given a large number of possible source-receiver combinations and a variety of scattering mechanisms to be exploited, this project focuses on the following two objectives as the top priorities: (1) parallelization of DBS-based migration, and (2) searching for small-scale heterogeneities in the mantle around the North American continent with P-to-P scattering. The DBS-based migration is a very time-consuming processing, but with the planned code parallelization, it will become possible to process a large volume of data. The P-coda part of seismograms, bounded by the direct P arrival and the PP phase, is suitable to be searched for potential scattered phases generated by S-to-P and P-to-P scattering. Because of travel times involved, S-to-P scattering can illuminate only the vicinity of earthquakes, but P-to-P scattering can probe all along the ray path of the direct P. The use of differential travel times with respect to the direct P limits the source-receiver distance to be shorter than ∼100°, but a number of good seismic sources (i.e., deeper than 100 km and Mw ≥5.0) around the Pacific will allow us to image scatterers in the mantle beneath the Northern Pacific, Central America, and possibly the Northern Atlantic.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69601
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Jun Korenaga.Mapping Small-scale Mantle Heterogeneities Using USArray.2016.