Submarine seismicity monitoring with distributed acoustic sensing near Santorini and Kolumbo Volcano

Submarine volcanoes and faults pose hazards to nearby populated islands, yet their inaccessibility limits monitoring efforts. The Christiana-Santorini-Kolumbo volcanic field is capable of generating devastating eruptions, earthquakes and tsunamis. The 2025 earthquake swarm near Kolumbo, causing the evacuation of thousands from their homes, underlines the need for accurate and real-time monitoring. We interrogate a 45 km dark fibre that extended from Santorini past the submarine volcano Kolumbo for two months in 2021, comparing the performance of the fibre with the existing monitoring network for earthquake detection and location. The detected quakes originated all over Greece, coming from any azimuth. We can reliably identify events, doubling the number of detections in the vicinity of the fibre and Kolumbo. For event location, the azimuthal coverage of the existing seismometer network outperforms the fibre, emphasising the importance of a nonlinear fibre layout. Our findings suggest that while the higher detection sensitivity of DAS leads to an information gain, the data analysis remains challenging. The data quality may be insufficient for automated workflows. The need for human input limits the potential of DAS for real-time monitoring, although the enhanced detection sensitivity in remote areas justifies the continued research of DAS for submarine volcano monitoring.