(25.1.2022) CeOS scientist Dr Florian Petersen is investigating earthquake hazards off the Sicilian coast during an expedition on the French research vessel NO Pourquoi Pas?
The study of submarine landslides and earthquakes is particularly challenging, as 70% of the Earth's surface is covered by the ocean. Compared to terrestrial remote sensing, satellite observations cannot usually be used in the ocean due to the attenuation of electromagnetic waves in the water. Therefore, the use of modern geophysical instruments and methods is necessary to identify and map structures and potentially hazardous areas on and under the seabed.
The Calabrian subduction zone on- and offshore Sicily holds great potential for strong earthquakes and associated hazards to society. The stresses that build up along this tectonic fault beneath the seabed have been poorly studied due to technical challenges.
As part of the EU ERC project FOCUS, an international team of 25 scientists led by Dr Marc-André Gutscher (Laboratoire Géo-Océan Brest) started the expedition on the French research vessel NO Pourquoi Pas? in mid-January 2022. Cooperation partners from Kiel University and the GEOMAR Helmholtz Centre for Ocean Research Kiel are also on board. Among the participants is the marine geophysicist Dr Florian Petersen from the Center for Ocean and Society CeOS.
The aim of the cruise is to investigate plate movements in the Ionian Sea and the resulting stresses on the seafloor. Thus, five GEOMAR ocean bottom seismometers, which had been anchored to the seabed for 14 months, were recovered off the eastern flank of the volcano Mt Etna. An integrative analysis of these new data and data from the CeOS-led RV Meteor Expedition M178 HazELNUT (November - December 2021) will be used to better understand the motion dynamics of Etna's sliding eastern flank. After data readout, these five ocean-bottom seismometers will then be deployed back to the same position on the continental slope off Etna to record earthquakes in the region for one to two years.
During the expedition, ten additional ocean bottom seismometers of the GEOMAR OBS pool, as well as five broadband seismometers of the French institutes Ifremer and LGO Brest, will be deployed on the seafloor between Sicily and Calabria. These will record the earthquake distribution in the area of the Calabrian subduction zone for one year. In addition, a network of acoustic distance loggers and a highly sensitive fibre optic cable, which were already installed during the first FOCUS expedition in 2020, will monitor the deformation of an active tectonic fault. The acoustic deformation data can be sent to the ship via acoustic data transmission and evaluated after the expedition. The geophysical investigations are accompanied by geological sampling of the seafloor. With the help of a piston corer, sediment cores up to 30 metres long will be taken along an important tectonic fault. Geochemical and palaeoceanographic analyses will provide information about the past and present activity of the fault. In addition, an unmanned underwater vehicle will be used during the expedition to map the seafloor in very high resolution.