Simulation of the records of the 27 March 2013 Nantou Taiwan earthquake using modified semi-empirical approach

It is seen that strong motion generation area plays an important role in the shaping of strong motion records at the observation point. Strong motion generation areas identified within the rupture plane of the 27 March 2013 Nantou, Taiwan, earthquake (M (w) = 5.9) have been modelled in this work. It is seen that all available records are at the surface which include site amplification terms. The modified semi-empirical technique effectively simulates records at rock site. The site amplification terms in all records have been removed using SHAKE 91 program and velocity input at each site. The observed records corrected for site amplification terms are further used for comparison with simulated record at the bedrock from several models. Once the observed records at soil sites are transferred at the bedrock, the next task is selection of final model that gives best fit records. Peak ground acceleration from simulated record at four sites is compared with that from corrected observed data. Since the semi-empirical technique of simulation is strongly dependent on various modelling parameters such as dip, strike, rake, rupture velocity and starting points of rupture, these parameters change iteratively in a specified range in a heuristic way to obtain best modelling parameters. The model giving minimum root mean square error (RMSE) is retained at final model. It is seen that minimum root mean square error of the wave form comparison has been obtained at four stations for the source model having single strong motion generation area. Strong motion records have been simulated at four different recording stations. Comparison of observed and simulated records has been made in terms of RMSE between simulated and observed acceleration records, velocity records and the response spectra at each of four stations. Comparison of waveforms and parameters extracted from observed and simulated records confirms the efficacy of the modified technique to model earthquake characterized by SMGAs.