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| Frequency dependent polarization analysis of ambient seismic noise recorded at a broadband seismometer in the central United States |
| Keith D. Koper1, Veronica L. Hawley2 |
1 Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
2 Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO 63108, USA |
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Abstract We present a new approach to polarization analysis of seismic noise recorded by three-component seismometers. It is based on statistical analysis of frequency-dependent particle motion properties determined from a large number of time windows via eigenanalysis of the 3-by-3, Hermitian, spectral covariance matrix. We applied the algorithm to continuous data recorded in 2009 by the seismic station SLM, located in central North America. A rich variety of noise sources was observed. At low frequencies (<0.05 Hz) we observed a tilt-related signal that showed some elliptical motion in the horizontal plane. In the microseism band of 0.05-0.25 Hz, we observed Rayleigh energy arriving from the northeast, but with three distinct peaks instead of the classic single and double frequency peaks. At intermediate frequencies of 0.5-2.0 Hz, the noise was dominated by non-fundamental-mode Rayleigh energy, most likely P and Lg waves. At the highest frequencies (>3 Hz), Rayleigh-type energy was again dominant in the form of Rg waves created by nearby cultural activities. Analysis of the time dependence of noise power shows that a frequency range of at least 0.02-1.0 Hz (much larger than the microseism band) is sensitive to annual, meteorologically induced sources of noise.
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Received: 07 June 2010
Published: 10 October 2010
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| Fund:the United States Geological Survey |
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Corresponding Authors:
Keith D. Koper
E-mail: kkoper@gmail.com
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