Publication Date:
2003-10-01
Description:
H/V spectral ratios from microtremors are used to retrieve the S-velocity structure from a single ambient vibration record, by using its relation to the ellipticity of the fundamental mode Rayleigh wave and the amplitude of observed H/V ratio. Constraints are needed in order to restrict the possible range of solutions, and the inversion is applied to sites where the thickness of the unconsolidated sediments is approximately known from borehole information. Within the uncertainty, the inverted structures agree well with the results from other S-wave measuring techniques such as downhole and cross-hole measurements, and the analysis of ambient vibrations measured on an array. The influence of the inversion uncertainty on site- amplification estimates for earthquakes is then investigated. For all inverted models, site response is computed for a large number of events, which allows to define the uncertainty by the apriori unknown source position and mechanism of a future earthquake. In most cases the variability between the results obtained for the different models is much smaller than the variability introduced by the unknown source position. The accuracy with which S-wave velocity structures can be retrieved from observed H/V ratios is therefore sufficient for an application of the method in seismic hazard analysis for a specific site.
Print ISSN:
1383-4649
Electronic ISSN:
1573-157X
Topics:
Geosciences
,
Physics
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