Strong Motion Modelling of the 1999 Izmit Earthquake Using Site Effect in a Semi-Empirical Technique: A More Realistic Approach

A devastating earthquake (M-w 7.4) struck near Izmit city, northwestern Turkey, on 17 August 1999. The relatively large size of this earthquake and site amplification conditions caused severe damage in the Marmara region as well as the city of Istanbul. The disastrous outcome of this large earthquake requires careful analysis of the seismic hazard including local site effects in this region. Therefore, the present work addresses the issue of local site effects and modelling of strong ground motion for this earthquake. We have estimated the soil effects using the horizontal-to-vertical (H/V) ratio. Furthermore, high-frequency records are simulated using a modified semi-empirical technique (MSET) by including estimated site effects. This modification will provide more reliable and precise simulated strong motion records. In the present study, strong ground motions are simulated at nine seismic stations in the epicentral range of 40-99 km. These stations were selected based on their recorded data quality. To validate the technique, we have compared the synthetic records with the observed records in terms of root mean square error (RMSE). This comparison includes time records, pseudo-acceleration spectra, mean period and predominant period. This comparison shows MSET has successfully simulated the 1999 Izmit earthquake.