Lithospheric Structure of the Dinarides-Adriatic Region From Ambient Noise Eikonal Tomography

Abstract

The Dinarides, a mountain range along the eastern edge of the Adria microplate, is the focus of the ongoing extensive geophysical research due to its complex tectonic features and importance in the evolution of the central Mediterranean. There are numerous open questions about the interaction and movement of Adria in the last 20 Ma with regards to surrounding tectonic units connecting collision to subduction beneath the Dinarides and possible fragmentation of Adria along its central part. In this study, we apply ambient noise eikonal tomography to refine our understanding of the Dinaric crust and uppermost mantle. We use 7 years of continuous data from regional seismic stations to calculate surface-wave phase velocities. Eikonal tomography is applied to both Rayleigh and Love waves, with independent inversions of local dispersion curves for each wave type. This approach produces detailed maps of vertically and horizontally polarized shear-wave velocities at different depths. Our results reveal intriguing insights: a prominent high-velocity anomaly in the upper crust, likely linked to carbonate rock deposits, and a significant low-velocity anomaly in the mid-lower crust, suggesting the presence of the deep orogenic root. Additionally, the high-velocity anomaly in the upper mantle suggests an underthrusting of continental lithosphere. Combined with a thicker crust and a slightly shallower lower-velocity anomaly toward the Pannonian Basin—may indicate low angle subduction or lithospheric delamination. However, horizontally polarized shear waves expose a localized low-velocity anomaly beneath the NW Dinarides that is not observed by vertically polarized waves, highlighting the complexity of the region's crustal dynamics.