The 7 April 2026 Reactivation of the Petacciato Landslide (Adriatic Coast, Italy): Field Evidence, Ground Deformation, and Rainfall-Triggering Conditions

The Petacciato landslide is a well-known, very large landslide located along the Adriatic coast of central–southern Italy and involving Plio-Pleistocene marine clay sequences with sandy intercalations. Reactivations have been documented since the early twentieth century and have occurred predominantly after prolonged rainfall periods. On 7 April 2026, a new reactivation event provided an opportunity to investigate this complex landslide system further. Displacements affected the A14 motorway and the Adriatic railway and led to the declaration of a national state of emergency. This study integrates geological, geomorphological, and hydrological information with recent European Ground Motion Service (EGMS) remote-sensing data and precipitation analyses to improve the understanding of the phenomenon. The findings indicate that the Apennine thrust front acts as a structural predisposing factor for the deep-seated landslide, whereas prolonged rainfall triggers reactivation. The analysis highlights the role of long-term cumulative rainfall as a primary driver of reactivation and the value of InSAR monitoring for evaluating continuous ground deformation, including during apparently dormant periods. The results emphasise how reactivation events can improve understanding of landslide behaviour and inform risk-management strategies.