Introducing SEASMO: SEismo-Acoustic Submarine Mediterranean Observatory

The SEASMO (SEismo-Acoustic Submarine Mediterranean Observatory) platform represents a major technological advancement in deep-sea multidisciplinary monitoring. Situated in the Ionian Sea at a depth of 3,450 meters, approximately 80 km SE offshore from Portopalo di Capo Passero, Sicily, the observatory was successfully deployed in October 2024 as part of the “Marine Hazard” project. Having now surpassed its first year of continuous operation, SEASMO has established itself as a cornerstone of real-time scientific data acquisition and environmental risk mitigation within the Mediterranean basin.

This sophisticated facility is the result of a strategic collaboration between the National Institute for Nuclear Physics (INFN) and the National Institute of Geophysics and Volcanology (INGV). The platform leverages the world-class deep-sea neutrino telescope KM3NeT/IDMAR infrastructure, utilizing two primary 100 km electro-optical cables to provide robust connectivity. This high-bandwidth link connects a submarine network of junction boxes equipped with Remotely Operated Vehicle (ROV) mateable wet connectors to an onshore laboratory, ensuring a stable power supply and instantaneous telemetry for uninterrupted data transfer.

A key feature of SEASMO is its complete integration into global and national monitoring frameworks. It is officially registered in the International Federation of Digital Seismograph Networks (FDSN) database under the station code MHPPL, operating as part of the KM3NeT Seismic Network (K3). Beyond its registration, the station’s data stream is directly integrated into the INGV seismic monitoring system, significantly extending the reach of the national seismic network into the offshore environment. Furthermore, the observatory is currently being incorporated into the operational workflow of the Tsunami Alert Center (CAT-INGV), providing essential offshore data that enhances the accuracy and timeliness of natural hazard alerts for the region. This latter is particularly important given that some of the most damaging historical earthquakes in the Mediterranean realm were generated by offshore active faults located close to the Sicilian coastline, including the “1693 Val di Noto earthquake” and the “1908 Messina earthquake” (M > 7). Nonetheless, the observatory is also located close to the poorly constrained Ionian Subduction Zone, whose potential to generate subduction-related megathrust earthquakes remains unclear.

The scientific payload of the station is specifically designed for high-resolution environmental and geodynamic characterization. Central to its mission is a 120-second broadband Ocean Bottom Seismometer (OBS) and a high-resolution hydrophone, capable of detecting frequencies with a 12.8 kHz bandwidth down to  1 Hz. This combination allows for the precise monitoring of seismic activity and the characterization of both natural and anthropogenic acoustic sources, providing critical insights into the impact of human activities on marine ecosystems. Additionally, the suite includes a Conductivity, Temperature, and Depth (CTD) sensor for tracking physical-chemical shifts in the water column, as well as detecting  high-resolution temporal  sea-level anomalies.

Throughout its operation, SEASMO has demonstrated the reliability of its automated data-processing routines, providing 24/7 real-time monitoring of the deep Mediterranean and offering a unique window into its geodynamics and acoustic soundscape, with considerable implications for marine science and hazard prevention.