Keywords: earthquake, accelerogram, response, spectra, seismological model, attenuation, hazard, GENQKE.

The ground motion and response spectral attenuation models form the key components in both deterministic and probabilistic seismic hazard assessment (SHA). It is the future trend in SHA to replace generic ground motion equations with more detailed models based on the physics of wave propagation, which would require multi-disciplinary knowledge such as seismology, geology, and so forth.

One promising way to achieve that is to employ the seismological model using a stochastic method, which is particularly useful for regions of low to moderate seismicity where recorded strong motion data are sparsely available. On the contrary to those regions of high seismicity such as California where strong motion records are abundant, and attenuation relationships are normally developed typically by regression of recorded ground shaking parameters. An important advantage of using the seismological model as the attenuation model in SHA is that each event can be assigned a set of filter functions.

Stochastic simulations of the seismological model which can be accomplished using program GENQKE was originally developed by the second author for generating earthquake accelerograms on rock sites [1]. This version which has been used extensively in research and hazard assessment does not take into account the important filtering mechanisms occurring within the soil sediments.

As soils behaves non-linearly when subjected to strong levels of ground shaking, it is more appropriate to account separately for site effects from bedrock and soil layers. In the new version of GENQKE to be introduced in this paper a site-response transfer function for modelling non-linear effects has been incorporated into the program forming a unique and distinctive feature. The new version of program GENQKE is particularly useful for site-specific seismic hazard assessment studies.

It is emphasized that the soil site response factor is not a single value for a specific site, as it depends on the level of soil damping and is, in turn, related to the shaking level at the soil-bedrock interface. Together with different resonant conditions, which are interactive effects arising between the earthquake scenario and site condition, the soil site response factor would vary for different scenario earthquake events. That represents a unique and distinctive feature of using the combination of the seismological model and site response transfer function as the ground motion attenuation model in SHA, in contrast to commonly employed attenuation models that are spatially smoothed, and therefore are unable to deal with individual local or site effects.

1

N. Lam, "Program GENQKE User's Guide: Program for generating synthetic earthquake accelerograms based on stochastic simulations of seismological models", Department of Civil and Environmental Engineering, The University of Melbourne, Australia, 1999.

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