Investigation of soil dynamic properties using horizontal-to-vertical spectral ratio for Eastern Pontides, Northeast Turkey

Turkey includes the major and active tectonic structures, which are the North Anatolian Fault Zone, the East Anatolian Fault Zone, Aegean extension region and Bitlis-Zagros thrust belt. Many destructive earthquakes have occurred on these tectonic structures and caused loss of life and property. Therefore, determining the soil properties that increase the destructive effect of earthquakes is an important parameter for the construction around these tectonic structures. In this study, it is aimed to investigate the soil properties (the soil predominant period, bedrock depth, Vs30) using 103 earthquake acceleration data (in the range of 3.5 <= Mw <= 6.8) recorded by 27 strong ground motion stations in the Eastern Pontides, Turkey. Moreover, the study area includes provinces (Samsun, Trabzon, Ordu, Giresun, etc.) with a high population density that may be affected by a destructive earthquake. The H/V spectral curve and the geometric mean of these curves were calculated for the earthquakes recorded by each station to assess the soil column. First, the predominant period and amplification factor of the soils were obtained from these curves. The predominant period values vary from 0.4 to 0.6 s and the amplification factor values change from 1.6 to 7.0. The stations with the largest period and amplification factors are 5301 and 5507, respectively. Furthermore, the soil vulnerability index (Kg), the bedrock depth, Vs30 values were obtained from these two parameters using empirical equations. Kg values are observed between 0.4 and 36. The highest Kg values were obtained at stations 5505 and 5507 in Samsun. The bedrock depth was calculated using twelve different empirical relations. The higher bedrock depth was obtained around Samsun-Giresun and the north of Erzurum. In addition to these evaluations, the empirical Vs30 relations were tested for the study area to determine the most suitable relation. As a result of all analyses, it was determined that Samsun province is a risky region in terms of soil. Detailed microzonation studies should be carried out to determine soil properties for this region.