Observations of Higher Mode Rayleigh Waves in Southern California
Abstract
This paper describes observations of higher mode Rayleigh waves in the microseism frequency band (0.05-0.2 Hz), using a year of seismic ambient noise data recorded on stations in Southern California. By using a minimum variance distortionless response (MVDR) processing, which has a high spatial resolution, the fundamental mode and the first mode of the Rayleigh wave are clearly localized both in slowness and azimuth. The higher mode is predominantly observed only along the Californian coast, whereas the fundamental mode is also observed at other azimuths (such as eastern US in August-November and north eastern US and Canada in December-February). Phase velocity estimates for both modes are retrieved and the dispersion curves agree very well with the theoretical dispersion curves based on a Southern California velocity model. The presence of a higher mode is also observed in the estimated coherence function between the stations, which is shown to be better modeled as a weighted sum of two Bessel functions of different spatial frequencies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.S13B..08M
- Keywords:
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- 7255 SEISMOLOGY Surface waves and free oscillations