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 s the results from all three methods agree, suggesting that the ambient seismic noise field is Rayleigh wave dominated. Between 10 and 30 s, while the general pattern agrees well, the results from FDPA and NSHV are persistently slightly higher (~2 per cent) and significantly higher ( > 20 per cent), 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 and tilt noise.
Bibliographical noteKAUST Repository Item: Exported on 2021-04-02
Acknowledged KAUST grant number(s): OCRF-2014-CRG3-2300
Acknowledgements: Instruments (data) used in this study were made available through EarthScope (EAR-0323309), supported by the National Science Foundation (NSF). The facilities of the IRIS Data Management System (NSF-EAR-0552316) were used to access the waveform and metadata required in this study. We thank Kris Pankow and William Holt Steve for providing helpful comments that improved this paper. This research was supported by NSF grant Cyber SEES-1442665 and the King Abdullah University of Science and Technology (KAUST) under award OCRF-2014-CRG3-2300. E. Workman acknowledges the support from a Chevron Fellowship.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
ASJC Scopus subject areas
- Geochemistry and Petrology