Advanced 3D seismic hazard analysis for active compression in the Adriatic Thrust Zone, Italy

The probabilistic seismic hazard assessment contains two ingredients: (1) the seismic source model with earthquake rates and rupture parameters for specification of the statistical distribution of earthquakes in time and space and (2) the ground motion model, for estimation of ground shaking level at a site for each earthquake rupture. The selection of these models significantly impacts the resulting hazard maps, and it can be challenging, particularly in seismotectonic regions where overlapping structures, sited at different depths, coexist. Eastern Central Italy is a well-known active compressional environment of the central Mediterranean with a complex tectonic structure with a lithospheric double shear zone. In this study, we propose a seismic hazard assessment to analyze the contribution of these two shear zones as overlapping multi-depth seismogenic volumes to ground motion at a given hazard level. We specifically focus on selecting relevant and applicable parameters for earthquake rate modeling, emphasizing the importance of defining rate computation and rupture-depth parametrization in hazard analysis. To achieve this, we utilized a seismotectonic- and catalog-based 3D adaptive smoothed seismicity approach following the methodology given by (Pandolfi et al. in Seismol Res Lett 95: 1-11, 2023). Finally, we demonstrated how this innovative 3D approach can identify with high resolution the individual sources' contribution with particular attention to the depth location of structures that strongly influence the ground motion. Moreover, combining seismotectonic data with seismicity avoids the challenges associated with structures with scarce geologic, geodetic, or paleoseismological data. Our result provides detailed insights into the seismic hazard within the Adriatic Thrust Zone.