A cabled, real time ocean bottom seismometer in the western Baltic Sea

Real-time seismic monitoring infrastructure requires permanent power and data transmission and therefore largely relies on land-based seismological stations. As a result, regional seismic monitoring of marine regions remains challenging with respect to event detection thresholds and hypocentral location accuracy. Particular challenges in seismic event monitoring in Northern Germany are the occurrence of both natural and anthropogenic events in the southern Baltic Sea and therefore the discrimination of event source types and, for tectonic events, hypocentral depth determination of earthquakes in the wider Tornquist zone region. Beyond that, seismic monitoring gained in recent years importance as an additional tool to monitor critical infrastructure as well as controlled and uncontrolled detonations of unexploded ordnance (UXO).

Recent advances in both offshore infrastructure and seismic offshore instrumentation systems provide a realistic opportunity to facilitate deployments of continuous, real-time ocean-bottom seismometers to significantly improve monitoring capabilities in offshore regions.

In summer 2025, we deployed a three component, cabled broad band Ocean Bottom Seismometer (Trillium Compact OBS) at the Darss Sill in the western Baltic Sea. At the site, the permanent MARNET monitoring station, operated by the Leibniz Institute of Baltic Sea Research in Warnemünde on behalf of the Federal Maritime and Hydrographic Agency (BSH) provides the infrastructure for a prototype deployment of a real-time OBS system. Seismic data is transmitted in near real-time to the data center at Kiel University and included in the real-time monitoring system. Over the past months, the OBS installation has been continuously improved, to enhance the data quality. The MARNET station also records oceanographic, biological and meteorological parameters that can be used to improve our understanding of ocean generated microseism with in situ data. While models and theories exist for microseism generation in the deep ocean, its generation mechanisms in coastal areas is still an open question.

We present first data observations and correlations and discuss challenges and opportunities for future offshore seismological monitoring in Northern Germany coastal region.