Investigating site-specific parameters for seismic hazard analysis in Büyükçekmece district of Istanbul: field study and HVSR analysis

The Büyükçekmece district of Istanbul, situated in a region near North Anatolian Fault, faces significant earthquake risk. This study aims to enhance our understanding of seismic hazards in Büyükçekmece by investigating site-specific parameters. We conducted a comprehensive field study involving seismic ambient vibration measurements at 56 selected locations. The horizontal-to-vertical spectral ratio (HVSR) method was employed to analyze the recorded data, and to obtain fundamental frequencies and approximate bedrock depths. These parameters offer insights into the local soil conditions and site amplification characteristics. The findings of this study reveal that the region exhibits intermediate to strong site amplification due to the contrast between alluvial deposits and Paleozoic bedrock. Peak frequencies ranged from 1.4 to 2 Hz, with amplification factors typically ranging from 1.5 to 2. Bedrock depths varied from 73 to 108 m, and average shear wave velocities to bedrock (V_Z) showed minimal variation (576 to 608 m/s). Correlations between fundamental frequencies (f₀) and V_S,30 values demonstrate the influence of soil properties on ground motion amplification. This study contributes crucial information for seismic hazard assessment and risk reduction in Büyükçekmece. The results provide valuable input for ground motion simulations and facilitate more accurate earthquake impact predictions. Understanding site-specific characteristics is crucial for improving the resilience of earthquake-prone regions such as Büyükçekmece, Istanbul. Overall, this research stresses the significance of site-specific investigations in improving our understanding of seismic hazard and risk.