The primary objective of the ERC Advanced Grant project FOCUS, funded from Oct. 2018 - Sep. 2025 is to test the use of laser reflectometry, to measure small (1 - 2 cm) displacements across faults on the seafloor and thus improve natural hazard assessment and early warning. For this project and seafloor experiment to be successful, a set of complimentary observational techniques (seafloor geodesy, seismology, ultra-high resolution morpho-bathymetric mapping, sediment coring) must also be applied. The first phase was to deploy a 6-km long fiber optic strain cable across an active submarine fault as well as a network of 8 seafloor geodetic stations to provide an independent measure of seafloor displacement across this fault. This work was accomplished during the FocusX1 expedition in October 2020 with R/V PourquoiPas? and the ROV Victor6000. During the expedition FocusX2 (13 - 28 Jan. 2022, Toulon - Toulon), we began a regional passive seismological experiment with deployment of 20 OBS (Ocean-Bottom Seismometers) (with an additional 9 LOT-OBS deployed during the FocusG2 expedition onboard the R/V TethysII in Aug. 2022), as well as permanent and temporary land-stations (from INGV). During FocusX2 we also performed micro-bathymetric mapping and sub-bottom profiling using the AUV idefX and acquired 14 sediment cores with a total length of 210 m.

During the expedition FocusX3, we recovered 29 OBS (14 from the Brest Ifremer/Geo-Ocean pool, and 15 from Geomar, Kiel), downloaded the data, and then redeployed 11 Brest OBS for another 6 to 12 month observation period. We deployed 13 seafloor geodetic stations in two networks: 8 Canopus instruments from Geo-Ocean (manufacturer iXblue/Exail) as well as 5 Sonardyne instruments (from Geomar, Kiel) to quantify displacement along the target fault offshore E Sicily. We deployed 1 ADCP lander current meter in order to detect sea bottom currents suspected of having disturbed the Focus fiber optic cable deployed in Oct. 2020. We also acquired an east-west CTD transect with 9 stations spaced every 3 km.