Characteristics of the Oceanic Lithosphere and the Propagation of Pn and Sn Seismic Phases

GSTDTAP

项目编号	1832371
	Characteristics of the Oceanic Lithosphere and the Propagation of Pn and Sn Seismic Phases
	Donald Forsyth
主持机构	Brown University
项目开始年	2018
	2018-08-01
项目结束日期	2020-07-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	221916(USD)
国家	美国
语种	英语
英文摘要	Earthquake recordings made by seismometers at the bottom of the Pacific Ocean contain important information about the structure and evolution of Earth's tectonic plates. When a plate initially forms near a mid-ocean ridge, for example, pods of melt can become trapped within the plate as it cools. These pockets of frozen melt have a different composition than the surrounding material and as such, alter how seismic waves propagate. This project plans to examine existing data recorded by two arrays of ocean-bottom seismometers deployed in the western Pacific. Novel observational and modeling techniques will be used to search for pods of melt emplaced during the formation of the tectonic plate. An important aspect of the project is to reconcile competing models of the lithosphere-asthenosphere boundary, that is, the transition from the rigid lithospheric plate to the more pliable rock below. Certain types of seismic observations suggest quite convincingly that the asthenosphere is mechanically weak relative to the overlying plate (lithosphere) but if this is the case, it is difficult to explain the existence of the seismic waves that are recorded. One hypothesis, which will be explored thoroughly, is that the addition of small-scale structures such as the frozen melt pockets can reconcile the two observations. The project supports the training of a postdoctoral investigator as well as undergraduate students. Pn and Sn waves - high frequency guided waves traveling within the lithosphere - provide one of the few ways that the fine-scale structure of the lithosphere can be probed. A detailed analysis of Pn and Sn waves recorded on two arrays of ocean-bottom seismometers (OBS) in the western Pacific will be carried out during this project. By examining the detailed waveforms in addition to the traditional approach of modeling the overall shape of the coda, it will be possible to resolve the overall velocity structure of old oceanic lithosphere better, the amplitude and scale of heterogeneities within the lithosphere, and the attenuation structure of the lithosphere. In turn, these observations will add to our understanding of the processes of lithospheric formation. The approach will be to combine detailed data analysis using new analytical techniques applied to more high quality Pn and Sn records than ever available before with extensive modeling of propagation of seismic waves in 3-D heterogeneous media. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/72965
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Donald Forsyth.Characteristics of the Oceanic Lithosphere and the Propagation of Pn and Sn Seismic Phases.2018.