7358 20250121112736.0 POSTER-2025-0026 Mahsa Onvani, Kris Vanneste Individual kappa calculation for BELSHAKE, site kappa and kappa gradient estimation across crustal domains in Belgium 2024 2024-11-27 This study explores the high-frequency attenuation parameter, κ (kappa), an important parameter in seismic hazard assessment. In this study κ was calculated using the classic definition by Anderson and Hough, which is based on the slope of the acceleration Fourier amplitude spectrum. To refine κ, we: Compared κ values with 𝑡∗ (t-star) values; Filtered induced and shallow seismic events (<8 km); Extrapolated site-specific κ0 to zero epicentral distance to isolate site effects; Validated results with global 𝑉𝑠30 expectations. To further investigate κ, three methods for estimating κ gradients and site-specific κ0 were evaluated: Free Kappa Gradient Method, Joint Kappa Gradient Method, Mixed-Effect Method. Each method offers unique advantages: Free Kappa Gradient Method being computationally efficient but sensitive to data quality; the Joint Kappa Gradient Method integrating multi-source data but constrained by optimization ranges; the Mixed-Effect Method providing robust statistical reliability for complex datasets. Performance comparisons across crustal domains using the Intraclass Correlation Coefficient highlight the trade-offs in simplicity, robustness, and accuracy among these methods. This comprehensive analysis enhances the understanding of crustal attenuation properties, contributing to improved seismic models and hazard assessments. 2BRAIN_BELSHAKE/ 2BRAIN_BELSHAKE/ 2BRAIN_BELSHAKE NO kappa, attenuation, site-specific kappa, kappa gradient, mixed effect method  102nd Journées Luxembourgeoises de Géodynamique (JLG) & EFEHR Scientific Session 2024 mahsa.onvani@ksb-orb.be https://www.ecgs.lu/102nd-jlg/ 1701479 http://publi2-as.oma.be/record/7358/files/Final version_EFEHR_Poster_Mahsa Onvani.pdf 20786 http://publi2-as.oma.be/record/7358/files/Final version_EFEHR_Poster_Mahsa Onvani.gif?subformat=icon icon 21399 http://publi2-as.oma.be/record/7358/files/Final version_EFEHR_Poster_Mahsa Onvani.jpg?subformat=icon-180 icon-180 CPOSTER