Spectral amplification from impulse response functions retrieved from ambient seismic noise: Adana Basin, Turkey

This study investigates the feasibility of extracting physically meaningful seismic amplification from Impulse Response Functions (IRFs) derived from Ambient Seismic Noise (ASN) in the Adana Basin, a deep sedimentary basin in southern Turkey. IRFs are retrieved by cross-correlating long-term noise recordings using a single virtual-source configuration, and the amplitude characteristics of Rayleigh-wave–dominated signals are analysed in the 2–10 s period range, which is particularly sensitive to basin-scale structure. Frequency-domain IRF amplifications exhibit a more consistent and physically meaningful relationship with basin geometry and sediment thickness than time-domain amplifications. Stations overlying the thickest sedimentary sections exhibit systematically higher long-period amplification, in agreement with the known basin geometry. Relative comparisons with observed earthquake amplitudes, basin-specific Ground Motion Prediction Equation (GMPE) estimates, and regional Peak Ground Acceleration (PGA) patterns reveal a consistent spatial correspondence, indicating that IRF-derived spectral amplitudes effectively capture dominant basin-controlled amplification trends. These findings highlight the potential of frequency-domain IRF analysis as a complementary tool for basin investigation and long-period seismic hazard studies, particularly in regions with limited earthquake recordings.