Determination of rayleigh wave ellipticity using single-station and array-based processing of ambient seismic noise

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Title Determination of rayleigh wave ellipticity using single-station and array-based processing of ambient seismic noise
Publication Type thesis
School or College College of Mines & Earth Sciences
Department Geology & Geophysics
Author Workman, Eli Joseph
Date 2016
Description We present a single-station method for the determination of Rayleigh wave ellipticity, or Rayleigh wave horizontal to vertical amplitude ratio (H/V) using Frequency Dependent Polarization Analysis (FDPA). This procedure uses singular value decomposition of 3-by-3 spectral covariance matrices over 1-hr time windows to determine properties of the ambient seismic noise field such as particle motion and dominant wave-type. In FPDA, if the noise is mostly dominated by a primary singular value and the phase difference is roughly 90° between the major horizontal axis and the vertical axis of the corresponding singular vector, we infer that Rayleigh waves are dominant and measure an H/V ratio for that hour and frequency bin. We perform this analysis for all available data from the Earthscope Transportable Array between 2004 and 2014. We compare the observed Rayleigh wave H/V ratios with those previously measured by multicomponent, multistation noise cross-correlation (NCC), as well as classical noise spectrum H/V ratio analysis (NSHV). At 8 sec the results from all three methods agree, suggesting that the ambient seismic noise field is Rayleigh wave dominated. Between 10 and 30 sec, while the general pattern agrees well, the results from FDPA and NSHV are persistently slightly higher (~2%) and significantly higher (>20%), respectively, than results from the array-based NCC. This is likely caused by contamination from other wave types (i.e., Love waves, body waves, and tilt noise) in the single station methods, but it could also reflect a small, persistent error in NCC. Additionally, we find that the single station method has difficulty retrieving robust Rayleigh wave H/V ratios within major sedimentary basins, such as the Williston Basin and Mississippi Embayment, where the noise field is likely dominated by reverberating Love waves.
Type Text
Publisher University of Utah
Subject H/V ratio; Interferometry; Polarization; Seismic Imaging
Dissertation Name Master of Science
Language eng
Rights Management ©Eli Joseph Workman
Format application/pdf
Format Medium application/pdf
ARK ark:/87278/s6004683
Setname ir_etd
ID 1344753
Reference URL https://collections.lib.utah.edu/ark:/87278/s6004683
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