As part of the SAFE-C project's ongoing effort to improve the detection and characterisation of seismicity in the North Sea, a Distributed Acoustic Sensing (DAS) interrogator (ASN OptoDAS) has been successfully deployed by GEUS on the CANTAT-3 submarine telecommunications cable.

Shortly after deployment, the system recorded its first seismic event: an M3.3 earthquake that struck Scotland on April 16, 2026. The signal, originating more than 800 km from the cable, was clearly captured across the fibre, demonstrating the remarkable sensitivity of DAS technology for regional seismic monitoring.

Waterfall plot of the M3.3 Scotland earthquake (April 16, 2026) recorded on the CANTAT-3 cable. Each horizontal slice represents strain rate converted to displacement measured along the fibre as a function of distance (y-axis, in metres) and time (x-axis). Coherent seismic energy is visible propagating across the full array length, more than 800 km from the earthquake epicentre.

The clarity of the signal at this range highlights the great potential of submarine fibre-optic infrastructure as a dense, long-baseline seismic network in an otherwise sparsely instrumented marine environment. This milestone marks a significant step forward for SAFE-C in integrating novel seismic data acquisition technologies into North Sea monitoring, turning existing telecommunications infrastructure into an operational distributed seafloor seismometer.