Pierre-Yves Raumer @pyraumer.bsky.social is a PhD student at Geo-Ocean in Brest. With a background in computer science, Pierre-Yves develops machine learning techniques to automate and improve the analysis of hydrophone records, teasing apart whale songs, icequakes and earthquakes in record time!

Jean-Arthur Olive @jaodynamics.bsky.social is a CNRS Research Scientist at ENS in Paris, and co-chief scientist on #GEODAMS. J-A uses mechanical models and geophysical observations to understand how the lithosphere deforms at tectonic plate boundaries, with mid-ocean ridges being his clear favorite.

Measuring travel time and knowing the speed of sound in water, the echosounder provides depth measurements along swaths, which we combine to create bathymetric maps, revealing underwater landscapes, submarine volcanoes, and ridges.

Using broadband OBSs, we will also carry out compliance measurements: that's looking at how the oceanic crust responds to changes in water pressure at the seafloor, due to tides and ocean dynamics. This should tell us whether magma is present at depth in the crust.

This local network will let us locate the events with high precision to characterize how mid-ocean ridge faults slip.

Once comfortably settled in the SOFAR channel, hydrophones record the sound made by earthquakes near and far, and let us relocate them with much better accuracy than distant seismometers on land.

They also record whale songs, and even the sound of icebergs grinding against each other! See for example this great explainer video from @noaa.gov : oceanexplorer.noaa.gov/explorations...

But last week we succeeded in recovering and re-deploying 1 beacon from the ridge network, and 1 from the transform network. The first year of data did not disappoint! #ToBeContinued

Some deployments can take up to 11 hours, as we go through trial-and-error on different target sites with the tripod hanging from the ship on a 2-km long cable.

We start by deploying the float containing the hydrophone from the back deck, then unroll the ~2 km long mooring...

We deployed 7 Ocean Bottom Seismometers (OBSs) to record earthquakes and other signals emitted by the Southeast Indian Ridge and the Amsterdam transform fault.

We will recover it at the location of our last hydrophone, West of Amsterdam, next week.

This glider is equipped with a hydrophone (48kHz) to record the underwater soundscape, and in particular the cetaceans (i.e., blue whales, fin whales, killer whales, sperm whales, etc.). The glider will navigate south and west of Amsterdam, diving down to 1000 m, driven by buoyancy changes.

In the meantime, Julie stayed on the Marion Dufresne, to manage communications between the pilot team in Brest and the team on the workboat.

In order to prevent the glider from colliding with the Marion Dufresne, it had to be launched at a certain distance. To do so, 3 brave members of our GEODAMS team, Anne, Séverine and Diane, boarded a workboat with 2 LDA crew members.