Evaluation of Local Site Conditions Using Ambient Seismic Noise Recordings: A Case Study from Ankara, Turkey

This paper aims to investigate the site response of the sediment characteristics and to perform seismic hazard studies in Ankara, Turkey through conducting short-period noise recordings of microtremor measurements at 352 project site locations on the Upper Pliocene to Pleistocene fluvial and particularly Quaternary alluvial and terrace sediments in the Ankara basin. The spectral ratios relative to a firm site reference station (SSR) and the spectral ratio between the horizontal and vertical components (HVSR) of the microtremor measurements at the ground surface have been used to estimate the fundamental periods and the amplification factors of the site. The results of this study identified three main factors that influence site response, namely, the age of the near-surface deposits, the sediment thickness and the non-linear soil behavior. In particular, the HVSR results showed that the variation of the fundamental period map agreed well with the maximum value of the amplification as well as with the seismic sediment characteristics that provided satisfactory estimates of the site response of soft deposits