The FocusX2 cruise project aims to set up an essential complementary experimental device for the FOCUS project (Advanced Grant project funded by the European Research Council to the tune of 3.5 M€ 2018-2023). As a reminder, the FOCUS project seeks to validate the technique of measuring seabed deformations using an optical fibre (laser reflectometry). The first part of the FocusX1 cruise project (classified P2 in 2019) took place in Oct. 2020 (8 days on the N/O Pourquoi Pas?). We carried out a site survey using micro-bathymetric mapping and visual observations (by camera) with the ROV Victor6000. Using the ROV, the 6 km Focus fibre optic cable was connected to the cabled observatory (TSS = Test Site South of the Catania Institute of Physics INFN-LNS) at a depth of 2050m. With the ROV, using a dedicated plough, we deployed a 6 km fibre optic cable and successfully buried it at 20cm depth for about half of the length. We also deployed 8 seabed geodetic stations to try and calibrate the observations of the fibre optic cable.

 During the FocusX2 cruise it was planned to :

1. Deploy 30 OBS (15 French and 15 German) to complement the INGV terrestrial seismic network to monitor seismic activity on active faults and even the subduction fault plane;
2. Carry out sediment sounder profiles (Chirp) and AUV sediment sounder profiles to specify the geometry of active faults, to image recent sedimentary deformations and to help in the selection of sedimentary coring sites;
3. Acoustic download of data from the 8 geodetic stations deployed in Oct 2020 on the northern termination of the North Alfeo Fault and potentially from the 6 geodetic stations deployed by Geomar in Nov 2021, on the continuation of the fault on the submarine flank of Etna;
4. The collection of sedimentary cores to conduct a paleoseismological study of turbidities, characterize the mechanical properties of the slope sediments, and analyze the interstitial fluids, coming from hydrothermal circulations through the fault that could modify its rheological behavior (serpentinization);
5. It was also planned to carry out a 2-day study of fluids in the water column by CTD Rosette.

Following the Covid-19 cluster on board the Pourquoi Pas on 3 January 2022, the duration of the cruise in the area was reduced from 18 days to 9 days. Thus, the objectives had to be revised downwards. The work of CTD Rosette was cancelled. The number of OBS deployed was reduced to 20. The download of seabed geodesy data was greatly reduced. There has also been a failure of the majority of the French seabed geodesy stations (Ixblue acoustic beacons purchased with ERC FOCUS project funds) which will require ROV intervention to recover them.