Kappa (κ) model for Kachchh region of Western India.

The empirical factor Kappa (κ), governs the rapid decay of spectral amplitude at high frequencies. It is one of the important parameters required in the simulations of earthquake strong ground motions. The present study estimates κ for 16 sites of Kachchh region of Gujarat (India). The Kachchh region is one of the most seismically active intraplate regions of the world that has experienced shocks of magnitude up to 8.0 in past. We have analyzed 159 accelerograms of 34 earthquakes of magnitude range 3.3-4.9 to estimate the κ. The estimated values of κ vary from 0.016 to 0.045 with an average of 0.023. Our results show no significant dependence of κ on distance (R) for the region. The analysis based on two sites shows that κ0 (κ at R = 0) is lower for the hard rock site (0.016) as compared with the value for the soft rock site (0.0201). One of the important observations of this study is that κ is not the source property for Kachchh region. The estimated values of the κ are useful for the stochastic simulation of earthquake strong ground motions. [ABSTRACT FROM AUTHOR]