How well can we detect tiny, human-made earthquakes?
Káldy et al, answer this question by testing automatic earthquake detection and localization with synthetic seismograms: a powerful validation tool!

Read more: doi.org/10.26443/sei...

If it all goes well, our now-complete observatory will be the first to document seafloor spreading and transform faulting events with geodesy, hydro-acoustics, and seismology! 🤞

Last, but not least, we also recovered and re-deployed an A-0-A pressure sensor, right in the middle of the ridge's axial valley. This state-of-the-art instrument corrects its own drift by regularly re-calibrating itself against an inner chamber where the pressure is known.

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

The core of the OHA-GEODAMS project is to measure active deformation for 3 years on the Southeast Indian Ridge and the Amsterdam transform fault. To this end, in February 2024, we deployed 15 acoustic beacons that have been pinging each other every few hours ever since.

Planning our upcoming deployments like they schedule sketches on Saturday Night Live
(with multiple new versions since that v1 😜) #GEODAMS

We also recovered and redeployed five hydrophones that were first deployed last year during the #GEODAMS 2024 cruise.

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

A few days ago, we deployed a Sea Explorer glider developed by ALSEAMAR and owned by ENSTA Bretagne at the location of our first hydrophone, southeast of Amsterdam island.

As we make our way to our study area, we map the seafloor under the ship! 🌊 Our multibeam echosounder sends acoustic waves to the ocean floor and records how much time they take to bounce back.

Getting closer to our site!

Yesterday @geodams.bsky.social

Meet the #GEODAMS 2025 team! ⚒️ @earth-science.bsky.social Right to left, back to front 👇

Today we were treated to spectacular views of Crozet's Possession Island and East Island, while the local penguins put on quite a show! 🐧🌤️⛰️

Happy new year from the R\V Marion Dufresne! Our journey began last year on xmas day, by heading straight South from La Réunion to the Crozet Islands.

Our target site is located on the Southeast Indian Ridge, near Amsterdam Island. But to get there, the R/V Marion Dufresne will first loop across the Southern Indian Ocean to do all kinds of oceanographic and geochemical measurements, and swing by the Crozet Islands and Kerguelen. #OBSAustral2025

The goal of #GEODAMS is to deploy and maintain the first-of-its-kind seafloor seismo-geodetic observatory across a mid-ocean ridge and adjacent transform fault, to document seafloor spreading as it happens on a time scale of a few years.

turns out the R/V Marion Dufresne is a spaceship

Hi! We are the OHA-GEODAMS team, a research project documenting how the Indian Ocean grows in (almost) real time. Between 2024 and 2027, we'll have 4 cruises to maintain a seafloor seismo-geodetic observatory across the Southeast Indian Ridge. We just started cruise #2, follow our adventures here!