Comparisons betweenVs30 and Spectral Response for 30 sites in Newcastle, Australia from collocated Seismic Cone Penetrometer, Active- and Passive-Source VS Data  

Authors / CoAuthors

Volti, T. | Burbidge, D. | Collins, C. | Asten, M. | Odum, J. | Stephenson, W. | HarrisPascal, C. | Holzschuh, J.

Abstract

Although the time-averaged shear-wave velocity down to 30 m depth (Vs30) can be a proxy for estimating earthquake ground-motion amplification, significant controversy exists about its limitations when used as a single parameter for the prediction of amplification. We make an extensive use of different methodologies as blind comparisons in order to question the applicability of amplification factor as defined by Vs30, for 30 sites in the Newcastle area, Australia. The multi-method approach includes past seismic cone penetrometer (SCP) and spectral analysis of surface waves (SASW), with newly acquired horizontal-to-vertical spectral ratio (H/V), passive source surface-wave spatial autocorrelation (SPAC), refraction microtremor (ReMi) and multichannel analysis of surface waves (MASW) data. We show that Vs30 can be related with spectral response but not necessarily with the maximum amplification. Transition zones within the geological boundaries may be important factors affecting site effects. Both Vs30 and amplification factor (AF) values are influenced by the velocity ratio between bedrock and overlying sediments and the presence of surficial thin low velocity layers (STL) (< 2m thick and < 150 m/s), but the velocity ratio is what affects mostly the AF. At 0.2 < T < 0.4 s, the AFs are largely influenced by surficial geology. For T > 0.5 s, amplification curves follow the order expected for hard to soft site classes. The SPAC and ReMi techniques have the smallest deviation from the average for all sites, corresponding to a factor of < 0.5 for > 75% of the data.

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• External PublicationScientific Journal Paper

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

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2018-07-06T00:40:18

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2015-01-01T00:00:00

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