Monitoring Earthquakes and Magmatic Intrusions in the Santorini–Amorgos Region Using Offshore DAS

Distributed Acoustic Sensing (DAS) is emerging as a powerful tool for seismic monitoring, enabling dense spatial sampling of seismic wavefields in offshore environments where conventional networks are sparse. This study focuses on the THETIS submarine fiber-optic cable operated by Vodafone, connecting the islands of Santorini and Kos across a tectonically and volcanically active sector of the South Aegean. The cable spans ~150 km, mostly parallel with major offshore fault systems and the Santorini volcanic complex. The study is particularly relevant in light of the ongoing volcano-seismic crisis in the Santorini–Amorgos region, reflecting coupled tectonic and magmatic processes. Since November 2025, continuous DAS recordings have captured abundant local seismicity, including numerous events originating from the Anydros–Anafi basin and from offshore and onshore Santorini island. The fiber geometry intersects several submarine faults, which produce distinct and coherent signatures in DAS earthquake record sections.

In addition to retrospective analysis, the DAS system is used operationally for real-time monitoring through edge computing at the remote interrogator site, combining  ML-based earthquake detection with fiber-optic geodesy based on low-frequency distributed acoustic sensing (LFDAS). This enables continuous on-site detection and tracking of earthquakes and possible strain-induced intrusion activity with minimal latency during evolving volcano-tectonic crises. A subset of decimated channels (~100 virtual stations) is streamed in real time to the National Observatory of Athens to support operational monitoring. We present preliminary results on data quality, earthquake detectability, machine-learning-based phase picking and location, and real-time DAS monitoring performance, highlighting the potential of DAS to improve monitoring capabilities and to provide new insights into fault structures and ongoing geodynamic processes in the region.