Site amplification estimated from strong motion records at Türkiye strong-motion stations using spectral separation technique

This study presents a nationwide assessment of seismic site amplification across Türkiye, based on 7191 strong-motion records from 757 earthquakes recorded at 462 stations of the Türkiye National Strong Motion Network. Using a spectral separation technique, contributions of source, path, and local site conditions were separated within the 0.5–20 Hz frequency range. The results indicate spatially and frequency-dependent amplification patterns across the country. Low-frequency amplification within the 0.5–1.3 Hz band is primarily observed at sites situated in sedimentary surface settings in eastern and southwestern Türkiye, whereas amplification within the 8.0–20 Hz band appears more evident in parts of southern Türkiye, including Hatay. Site amplification factors were evaluated across four geological units and five site classes defined by the National Earthquake Hazards Reduction Program (NEHRP). Quaternary units and sites classified as Class E exhibit stronger low-frequency amplification, whereas Paleozoic units and Class C–D sites tend to show higher-frequency responses. A relationship between Vs30 (time-averaged shear-wave velocity in the upper 30 m) and amplification is observed, particularly within the 0.5–1.3 Hz frequency band. These findings contribute to understanding of local site effects and provide insights relevant to seismic hazard assessment, urban planning, and resilient structural design under local ground conditions in Türkiye. © 2026 Elsevier Ltd.