Active and passive Slabs in the Central Mediterranean imaged with surface wave tomography

The tectonic evolution of the Central Mediterranean is heavily influenced by multiple subduction systems with intricate geometries. While numerous seismic studies have provided insights into these subduction zones, key aspects of their dynamics remain unresolved. To advance our understanding, it is essential to analyze the interplay between crustal structures, the mantle lithosphere, and the underlying asthenosphere in a coherent model. Surface wave tomography has established itself as a critical method for delineating the lithosphere-asthenosphere interface and subducting slabs without relying on local seismic sources.

This research is based on a combined inversion of ambient noise and earthquake-derived data to develop a comprehensive 3D shear-wave velocity model for Southern Italy and the broader southern Central Mediterranean. The inversion utilizes an extensive dataset comprising 95,000 Rayleigh wave phase velocity dispersion curves and 40,000 Love wave curves. These data, extracted from ambient noise cross-correlations (2–100 s) and earthquake-based two-station measurements (8–250 s), underwent rigorous quality control to ensure data integrity. Integration of the datasets was achieved through a correction factor derived from overlapping inter-station paths.

Azimuthally anisotropic Rayleigh wave phase velocity maps were generated using a regularized least-squares approach and subsequently inverted for depth using a stochastic particle swarm optimization algorithm, enhancing the reliability and precision of the resulting model.

The resulting 3D velocity model reveals significant subsurface features, including the Calabrian and Hellenic slabs, and identifies a slab tear beneath Sicily. Additionally, the model provides detailed insights into the transition from the Ionian lithosphere to the Calabrian slab and highlights a seismically inactive slab segment beneath western Sicily.