Ufuk Aydin, Caglar Ozer, Erdem Bayrak

Seismic absorption coefficients and soil dynamic characteristics: implications for seismic hazard in Erzurum Basin, Türkiye

Abstract
In this study, the seismic absorption coefficients  and nine seismic sub-regions for seismic hazard that may affect the Erzurum city centre were determined. Recurrence periods and the probabilities of occurrence of earthquakes above a specified magnitude threshold within a given time window were quantitatively estimated for each sub-region. The relationship between the seismic absorption coefficients and the probability of major earthquakes was analyzed, and the potential effects of these seismogenic structures on the Erzurum city centre were evaluated. Following the seismic hazard-based regionalization, the Erzurum city centre was further subdivided into eight sub-regions. A total of 24 microtremor measurements (three per sub-region) were conducted to characterize the dynamic soil properties within these sub-regions using passive seismic data. The seismic absorption coefficients, magnitude distributions and variations in dynamic soil characteristics of Erzurum were assessed regionally. Seismic hazard analyses conducted for nine different areas particularly highlighted the potential of major fault zones around Erzincan, Varto, and Bingol, specifically the North Anatolian Fault Zone and East Anatolian Fault Zone, to generate high-magnitude earthquakes. Seismic attenuation analyses revealed an average absorption coefficient of 0.02475 across the region, with values lower in the eastern and western sections and higher in the northern and southern sections. These results indicate that seismic energy distribution in the region has a heterogeneous structure and that geological features play a decisive role in this process. Microtremor measurements showed that soil amplification factor in the Dadaskent region reached significant values below 1 Hz, indicating that this area is critical in terms of earthquake-soil-structure interaction. Consequently, the combined effects of high amplification and regionally variable attenuation characteristics imply an increased seismic hazard potential for the Erzurum city centre, particularly in zones with unfavourable local site conditions.


Doi https://doi.org/10.5200/baltica.2026.2.1

Keywords Seismic wave attenuation; microtremor; local site effects; b-value

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