Deployments of geophysical instruments during the first RHUM-RUM Cruise Sep.-Oct 2012, aboard Marion Dufresne (cruise MD192, Leg2)
Films produced by Emmanuel Pons of the University of La Réunion.
Our main type of instrumentation: Ocean-bottom seismometers record the subtle motions of the ocean floor until we return in 2013. We are particularly interested in recording waves from earthquakes that occurred thousands of kilometers away, which illuminate the mantle deep beneath La Réunion. We are also interested in smaller regional earthquakes and the daily noise on the ocean floor.
Bathymetry: the ship constantly surveyed the depth and shape of the ocean floor by sending and recording acoustic pings. Only a small fraction of the world's ocean floor has been mapped with a state-of-the-art multi-beam bathymeter such as the one on the Marion Dufresne, and new discoveries are common. Our colleague Dass Bissessur from the Mauritius Oceanography Institute explains the discovery of a picture-perfect seamount (in French).
The magnetometer measures the magnetization of the seafloor, which gives information about how and when the ocean basins formed. It gets towed behind the ship and recorded constantly, except when the ship stopped. Here the sailors are redeploying the magnetometer after the end of a seismometer deployment.
The only instrument recovery during the cruise: an absolute pressure sensor was tested on the seafloor for several hours by our colleague Wayne Crawford from IPG Paris. Next year, we will return to recover our 57 ocean-bottom seismometers in a similar way.