3D geological and velocity modeling of the Northern Adriatic region for seismic hazard assessment

The Marche offshore, situated at the leading edge of the Northern Apennines compressional structures, is a key area for investigating seismic activity and its interplay with offshore operations. The Mw 5.5 earthquake of November 9, 2022, and the most recent Mw 4.2 of October 6, 2025, brought renewed attention to this region, highlighting the ongoing seismicity along frontal thrusts and reinforcing the need for detailed seismic hazard investigations in the area.

Within the framework of the SPIN project (Test delle buone pratiche per lo Studio della Potenziale INterazione tra attività offshore e pericolosità naturali - Best practice testing for the Study of Potential INteractions between offshore activities and natural hazards), the Italian National Institute of Geophysics and Volcanology (INGV) has built an unprecedented, high-resolution 3D geological and velocity model of the whole Northern Adriatic basin and its adjoining onshore domains.

The study adopts an integrated workflow that combines various data types, including publicly available data and, primarily, confidential 2D and 3D seismic surveys and well-log data granted by ENI S.p.A., as well as geological maps and technical reports.  Interval velocities for key seismic-stratigraphic units were estimated through analysis of check-shot and well-log velocity data, enabling a robust depth conversion. The resulting 3D geological model extends to depths of up to ~70 km, incorporating regional tomographic studies and crustal-scale geodynamic reconstructions

This comprehensive three-dimensional framework provides a precise reconstruction of the geometry and kinematics of the northern Apennine thrust front, allowing also the evaluation of the interaction between Mesozoic inherited structures and more recent compressional fault systems. This approach provides new insights into the segmentation of the thrust front and the spatial distribution of potentially seismogenic structures in this sector of the Adriatic domain.

Using the identified fault systems, the mapped surfaces, and the velocity model, seismic shaking scenarios were generated through standard ShakeMap simulations and advanced hybrid numerical methods for broadband wave propagation in heterogeneous 3D media.

The study demonstrates that multidisciplinary modeling at the crustal scale is essential for improving the reliability of seismic simulations and refining seismic hazard assessments in complex offshore-onshore contexts.