Linking Stress Drop and Slip Heterogeneity to Assess Source Rupture Directivity for Earthquakes in Central Italy

ABSTRACT In this study, we examine the relationship between Brune stress drop and fault slip where the stress drop is estimated using the Empirical Green's Function (EGF) method and slip distribution is derived from seismic and geodetic data inversion. We also explore correlations between stress drop and a series of rupture parameters, including rupture velocity, asperities and their strength, as well as hypocentral location. We assess how these factors influence both the manifestation of rupture directivity and its spatial characteristics along the fault. This approach is applied to two earthquake sequences in Central Italy: the 2009 L'Aquila event and the 2016 Amatrice–Visso–Norcia mainshocks. We find that large‐slip patches lead to significant ground motion amplification, pronounced rupture directivity and higher stress drop in near‐source regions. These findings can enhance ground motion prediction in areas where complex source effects play a critical role.