On the Use and Misuse of “kappa” in the Stochastic Simulation of Ground Motion: Example Applications Using the EUROSEISTEST Database Records
Wednesday, 17 December 2014
“Kappa” has always been an important input parameter in most codes commonly used for the stochastic simulation of strong ground motion. It is the one parameter controlling the decay of the high-frequency part of the seismic spectrum and, although still debated, it is most frequently related to the site effect. In the present study, we use the lower-magnitude earthquake records in the EUROSEISTEST database (http://euroseisdb.civil.auth.gr) to compute site-specific “kappa” and then predict larger-magnitude earthquake records through stochastic simulations. We emphasize the proper use of “kappa” when it is combined with empirical transfer functions that have resulted from Standard Spectral Ratios (SSR) or Horizontal-to-Vertical Spectral Ratios (HVSR), as these functions already include part of the “kappa” effect. Furthermore, we discuss the scatter in “kappa” measurements in relation to the site class and the distance to the earthquake source, and present examples of the possible effect of such scatter in simulated ground motion.