Characterisation of an Urban Site by Ambient Noise HVSR Method:Resonance Frequencies and Site Amplifications

摘要

The resonance frequencies and site amplifications of a proposed developmentsite on the Penrith campus of the University of Western Sydney have been studied bymeans of a non-invasive ambient noise Horizontal to Vertical Spectral Ratio (HVSR)method. Unlike other non-invasive surface wave techniques (such as the SASW,MASW, CSW etc) which require an array of connected sensors, the HVSR techniqueis a single station method requiring no such connection. Moreover, the HVSRtechnique is a passive method in relying only on the ambient microtremors caused bynatural events (tides, large-scale meteorological conditions) and cultural activities(industrial machinery, cars and trains) as excitation sources. This paper presents onepart of a study which aims to characterise the site effects and layered soilstratigraphy of a development site at the Penrith campus. In this study, measurementsof the ground responses in the vertical and two orthogonal horizontal directions werecarried out using a lightweight battery operated, wireless 3-component digitaltomograph. The estimated HVSR curves, the resonance frequencies and siteamplifications, and interpretations of the results obtained for the site are discussed.The experience from this study indicates that this could be a low-cost and attractivetechnique having a great potential in near surface geotechnical characterisation ofurban sites. Further investigation is currently being undertaken to study its efficiencyand accuracy in establishing the S-wave velocity profiles and soil stratigraphy of thesite by inverse analysis of the HVSR curves.