科研之友
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摘要
We present an approach for seismic noise which improves Rayleigh-wave ellipticity estimates by reducing the influences from body waves and Love waves. The method requires three-component seismographs and uses the phase-shift information between the vertical and horizontal components. We select data that show the phase-shift of about 90 degrees in order to separate Rayleigh waves from body waves and Love waves. In comparison to the usual H/V approach, the estimates for Rayleigh-wave ellipticity are systematically different by about 20 per cent because the existence of S waves and Love waves systematically increases horizontal amplitudes. The differences in the inverted S-wave velocity structure reach up to about 20 per cent in the upper 20 km. The method is limited to a relatively low-frequency range, below 0.3 Hz, as the 90 degrees phase-shift peaks become difficult to identify above 0.3 Hz. Despite this limitation in the frequency range, this approach can improve the S-wave velocity structure in the upper 5-10 km, which should lead to a better prediction of long-period ground motions for periods of about 5-10 s. An improved prediction of such long-period ground motion is important for hazard mitigation in the world's metropolitan areas with high-rise buildings. This approach is applied to the structure in the broader Los Angeles basin in Southern California and improvement of the reference velocity structure in the upper 5-10 km is demonstrated.
- 出版日期2013-4
