Autocorrelation of Seismic Ambient Noise and P-wave Coda for Crustal Structure

GSTDTAP

项目编号	1839322
	Autocorrelation of Seismic Ambient Noise and P-wave Coda for Crustal Structure
	Robert Nowack (Principal Investigator)
主持机构	Purdue University
项目开始年	2019
	2019-02-15
项目结束日期	2021-01-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	121740(USD)
国家	美国
语种	英语
英文摘要	This project develops new methods for exploring how to use noise in seismic measurements to better image the Earth's crustal structure. These new methods are important since many areas of the world are aseismic and controlled man-made seismic sources are expensive. So new ways to use existing nonseismic signals, called ambient noise, to image the Earth can be used in many places, such as the Midwest. Twelve portable seismic stations will be deployed centered on the Earthscope seismic station SFIN over a several month period. These methods will then be applied to selected seismic stations in the upper part of the central Midwest with similar ambient noise characteristics to test the consistency of the approach and image a stretch of the crust from Iowa to Ohio. They will compare this work by doing the same for a the recent "Large-N" IRIS Community Wavefield Demonstration Experiment in Oklahoma. Since the Oklahoma array is comparable in aperture to the small-scale array at SFIN, the relative performance of the two arrays will be compared. The broader impacts of the proposal come from improvements in the methodology and implementation of ambient seismic noise technologies and extending these to seismic body-wave imaging. Utilizing the deployed seismic stations, K-12 activities and displays will be developed to engage younger students with recent new developments in seismology, including the recording of ambient seismic noise and P-wave coda from earthquakes. Seismic interferometry for body-waves is studied for crustal reflectivity using autocorrelations of ambient noise and the P-wave coda from earthquakes. The autocorrelation stacks of ambient noise results in virtually coincident sources and receivers and effective zero-offset reflection seismic traces. The influence of the ambient noise distribution on the autocorrelation stacks can be approximately estimated using polarization analysis on single three-component stations, but a more comprehensive analysis can be done using beamforming from a small seismic array. Twelve portable seismic stations will be deployed over a 10-km spiral-arm array configuration centered on the Earthscope seismic station SFIN over a several month period, and beamforming will be performed to estimate the regional illumination distribution of the autocorrelated ambient noise signals to obtain illumination corrections. These will then be applied to selected seismic stations in the upper part of the central Midwest with similar ambient noise characteristics to test the consistency of the approach and to obtain an effective zero-offset linear section of crustal reflectivity. Several autocorrelation techniques are investigated to provide higher resolution estimates of crustal reflectivity, including tuned temporal and frequency normalizations, phase correlations, and time-frequency phase weighted stacks of the correlated ambient noise. Correlated P-wave coda of regional and teleseismic earthquakes are also investigated, where stacking over events are used to reduce the effects of source side scattering to better image the receiver side crust. The researchers will compare this array with the Large-N IRIS community wavefield experiment in Oklahoma for for the estimation of virtual crustal reflectivity from autocorrelated ambient noise. 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/212971
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Robert Nowack .Autocorrelation of Seismic Ambient Noise and P-wave Coda for Crustal Structure.2019.