Kocaeli Journal of Science and Engineering, vol.4, no.2, pp.160-170, 2021 (Peer-Reviewed Journal)
Amplification and predominant periods of soils in Düzce Basin were investigated by analysing the data sets of last two major earthquakes and aftershocks of Kocaeli and Düzce earthquakes occurred in 1999 with a magnitude of Mw:7.4 and Mw:7.2, respectively. Two different methods named horizontal/vertical spectral acceleration ratio (HVSAR) and soil-to-rock Response Spectral Acceleration Ratio (RSAR) were used to determine soil amplifications for various periods in Düzce Basin. The data set includes 31 strong gorund motion records from five strong ground motion stations. It was found that the site amplifications at stations are directly related to the local geology underlying the stations. Averaging the residuals between the predicted and observed PGAs resulted in soil amplification from 1.33 to 2.33. The HVSAR method presented soil amplification values between 2.7 and 10 and predominant period values between 0.4 and 0.7 s. Soil amplification values from 1.5 to 14 and predominant periods from 0.5 to 0.8 s were obtained by the RSAR method. High site amplifications and predominant periods mainly depend on the thickness of lithological variances accompanied by low physical and geotechnical properties of alluvial deposits.