Combining Seismotectonic and Catalog-Based 3D Models for Advanced Smoothed Seismicity Computations

The new generation seismic hazard maps use 3D seismotectonic fault models, which are more consistent with the actual nature of faults, whereas the classical models based on earthquake catalogs only utilize a 2D representation of the seismicity. Although the former provides more reliable information on seismogenic structures, the latter can deliver trustworthy seismicity rates easily. Therefore, it is necessary to combine both the approaches to create a high-quality seismic hazard assessment model. This study proposes an innovative approach using smoothed seismicity methods that can be advantageous in all contexts with available 3D fault models and high-quality seismic catalogs. We applied our method on the Adriatic Basal Thrust (ABT) in eastern central Italy—a lithospheric-scale active contractional structure with a well-constrained 3D geometric–kinematic reconstruction and a related high-quality catalog. Our new 3D algorithm was applied to smooth the ABTseismicity on the grid, resulting in a 3D earthquake rate model that also provides rupture parameters such as strike, dip, rake, and seismogenic thickness. Our approach is particularly useful for complex seismotectonic settings, such as in cases of lithospheric shear zones, subduction planes, and overlapping multidepth seismogenic volumes.