Directional Variability of Ground Motion Components: Toward an Integrated approach for Seismic Hazard Assessment

Ground motion parameters exhibited by earthquakes display significant variability when considering the simultaneous interaction of horizontal components and their orientation within the horizontal plane. Traditionally, these effects were analyzed independently and correlated probabilistically. Instead, this research presents an alternative approach that integrates Cartesian ground motion components into a unified expression using a dataset from the Italian and Balkan peninsulas. Peak Polar Normalized rotation-independent ordinates now capture variability across all orientations. The processed data has been finally clustered by using an unsupervised algorithm to identify possible correlations. While no definitive geographic standardization or conclusive patterns emerged, the simplified ellipsoidal model revealed that instantaneous polar peak acceleration is 25–45% higher than orthogonal components.