T-waves, explosions, and submarine: an overview of the Danish kingdom's seas soundscape

Fiber Optic Sensing and Distributed Acoustic Sensing (DAS) are emerging technologies that are revolutionizing the way we monitor the acoustic and seismic wavefield in the oceans. By turning tens of kilometers of fiber-optic cables into seismo-acoustic sensors with meter-scale spacing, DAS enables unprecedented spatiotemporal monitoring of submarine soundscapes. 

GEUS was granted access to four major submarine telecommunication cables with available dark fibers: AURORA between the island of Bornholm and Germany; two segments of Cantat-3, one north of the Faroe Islands and another in the North Sea; and the SHEFA-2 cable between the Faroe Islands and Shetland. 

In this presentation, we review various seismo-acoustic signals detected on the four cables, spanning natural and anthropogenic sources. We will dive deeper into the analysis of a submarine explosion in the Baltic Sea to see how a hybrid seismic network comprising DAS and standard seismometer measurements helped characterize the source. We will also present the results of our investigations into the March 10, 2025, M6.5 Jan Mayen earthquake, focusing on its strong T-wave recorded throughout the Greenland and the Norwegian Seas basins.