VS30, site amplifications and some comparisons: The Adapazari (Turkey) case

Abstract The aim of this study was to investigate the role of V S 30 in site amplifications in the Adapazari region, Turkey. To fulfil this aim, amplifications from V S 30 measurements were compared with earthquake data for different soil types in the seismic design codes. The Adapazari area was selected as the study area, and shear-wave velocity distribution was obtained by the multichannel analysis of surface waves (MASWs) method at 100 sites for the top 50 m of soil. Aftershock data following the Mw 7.4 Izmit earthquake of 17 August 1999 gave magnitudes between 4.0 and 5.6 at six stations installed in and around the Adapazari Basin, at Babali, Şeker, Genc, Hastane, Toyota and Imar. This data was used to estimate site amplifications by the reference-station method. In addition, the fundamental periods of the station sites were estimated by the single station method. Site classifications based on V S 30 in the seismic design codes were compared with the fundamental periods and amplification values. It was found that site amplifications (from earthquake data) and relevant spectra (from V S 30) are not in good agreement for soils in Adapazari (Turkey).