Estimation of Near-Surface Attenuation in Bedrock for Analysis of Intraplate Seismic Hazard

Document Type : Structural Earthquake Engineering

Authors

1 Centre for Earthquake Engineering Research (CEER), Department of Civil Engineering, University of Hong Kong

2 Department of Civil and Environmental Engineering, The University of Melbourne

3 Department of Civil Engineering, The University of Hong Kong

Abstract

The significance of near-surface attenuation in bedrock, as distinct from attenuation in unconsolidated soft soil sediments, has been identified. The k parameter, which characterizes the extent of this attenuation mechanism, is generally difficult to measure, particularly in regions of low and moderate seismicity. Empirical correlation of k with the near-surface shear wave velocity parameter in rock has been developed using global information obtained from limited independent studies. The influence of shaking intensity on the value of k has been found to be negligible in conditions that are consistent with the average seismicity of Australia (as also for other intraplate regions). Thus, adjustment in the value of k to account for variations in earthquake magnitude, or the intensity of ground shaking, has not been recommended for intraplate conditions. In parallel with the empirical correlations, values of k have also been obtained from calibration analyses employing stochastic simulations of the seismological model, along with onedimensional non-linear shear wave analyses of the rock layers. Good agreement in the values of k obtained from the different approaches has been demonstrated. The correlation of k with the near-surface shear wave velocity of rock, as recommended in this paper, has thereby been reaffirmed.

Keywords

Journal of Seismology and Earthquake Engineering
Volume 7, Issue 3 - Serial Number 3
October 2005
Pages 159-173

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