SITE CHARACTERIZATION OF STRONG MOTION STATIONS IN NORTH MACEDONIA

<p>This study focuses on the site characterization of strong motion stations in North Macedonia using H/V spectral ratio analysis of both microtremor measurements and recorded earthquake data. It presents a methodology for calculating the H/V spectral ratio from earthquake recordings, with results compared to those obtained from microtremor measurements (available for most stations) to assess consistency and reliability. Currently, thirteen strong motion stations are operational across the country, with additional data available from thirteen non-operational stations. Several sites have been previously investigated through geophysical surveys and borehole geotechnical studies, which are also utilized in this study for comparison with the newly conducted H/V analyses. The analysis emphasizes the influence of local site conditions on recorded ground motions and identifies potential site amplification effects. These findings will serve as a basis for defining appropriate frequency ranges in the calculation of the high-frequency decay parameter, kappa (κ), for the territory of North Macedonia. Future work will explore the potential correlation between the fundamental site frequency and the site-specific attenuation component (k₀) of kappa, aiming to improve the understanding of local site effects. These insights could contribute to the refinement of site classification schemes for the next generation of Eurocode 8.</p>