The site effect assessment of September 26, 2019 Marmara Sea darthquake (5.8 Mw) in the vicinity of Istanbul

The main purpose of this study is assessing the site effects created by Mw 5.8 September 26, 2019 Istanbul (Silivri) Marmara Sea earthquake struck regarding the data of Strong Ground Motion Stations of Turkey (TR-NSMN). Within this scope accelerograms that are obtained from 46 stations were analyzed by using 3-components response spectral ratios. 46 sensors have detected the earthquake at over 10 Gal (cm/sec(2)) within the 150 km radius due to the strong shaking. Highest ground acceleration (84. 9 gal) measured at 3412 coded station in Istanbul (Buyukcekmece) station, about 34.5 km far from the epicenter. Sorting out the instrumental data (Shear wave phase parts) has yield precious experimental results indicating site amplifications factor 3-12 at 0.3-1.5 s predominant periods corresponding even further 100 km away from the epicenter in Kocaeli, Bursa and Balikesir stations. Besides, theoretical horizontal-to-vertical spectral ratios were calculated for the significant stations having solid geotechnical data for comparison with instrumental data. Thereby, obtained experimental results such as building effects causing to feel the long period oscillations over 1 s predominant period with the range of 10 to 13 amplification factor (Kocaeli) and near field (<30 km) site effects originated from shallow lithology at Istanbul and Yalova stations might reveal crucial outputs in order to mitigate the possible seismic hazards studies.