SENSITIVITY OF GROUND MOTION SIMULATIONS TO EARTHQUAKE SOURCE PARAMETERS

Abstract

Strong motion data provides an important mean of understanding the characteristics of earthquakes as it provides crucial information related to the frequency content and duration of ground motion. The sensitivity of the strong ground motion to source effects, variations in the transmission path and the effect of local site conditions provides useful insight with respect to response of built up environments to earthquakes. In this regard it is important to generate synthetic data for various earthquake environments in regions where strong motion data is not available. In this study three reference scenario earthquakes are used for generating synthetic data for the Dehradun city at the bed rock level using a stochastic method. The uncertainties related to the source and path effects in the simulated data are needed to be resolved and that is where the study becomes fruitful. For this purpose, 31 scenario earthquakes are modeled for each reference scenario by changing the various source and path factors. The variation in mean ditThrences of the absolute values of PGA and PGV for the reference scenario and each scenario earthquake gives a good insight into the sensitivity of these simulations to the various parameters. The source duration was found to be the most sensitive parameter among those considered. The ground motion simulations showed negligible sensitivity effect to change in site diminution factor kappa. Among others, the stress drop (Ac) and the attenuation parameters Qo and ij were found to have significant effect on the ground motion simulations. In the different simulations the frequency range of 7-17 Hz was found to be critical in terms of spectral accelerations.