Fluid-Induced Fault Reactivations in Strike-Slip Regimes: Temporal Constraints from GNSS and Seismological Analysis in the Peloritani Mts. and Aeolian Archipelago (Central Mediterranean)

Fluids modify mechanical properties of rocks, such as shear strength and strain behavior. We investigate the deformation timing and the magnitude of seismic events during fluid-induced fault reactivation in strike-slip systems across the Peloritani Mts (Northeastern Sicily) and Aeolian Archipelago through GNSS and seismological data analysis. Results reveal a crustal-scale NNW-SSE trending right-lateral transtensional deformation zone across the Peloritani Mts and its offshore prolongation (here defined as GPTLFS), and WNW-ESE to NW-SE right-lateral transfer zones located in the western and central sectors of the Aeolian Archipelago. During 2021, the eastern sector of the GPTLFS underwent a significant velocity increase relative to the fixed western segment, varying from 1.6 ± 0.28 mm/y (pre-2021 baseline) to 3.3 ± 0.99 mm/y during the event year. The acceleration of the eastern sector of the GPTLFS was accompanied by increased seismic strain release and was temporally correlated to the fastest ground inflation on Vulcano Island (central Aeolian Archipelago) that, in turn, coincided with the highest CO₂ flux emission on the island. This correlation, along with evidence of gas emissions in the Peloritani Mts, suggests that enhanced fluid circulation lubricated fault surfaces, thereby facilitating strain release along the GPTLFS. The fluid-induced slip acceleration was sustained for a nine-month period and marked by frequent low-magnitude earthquakes.