Working on board with OBS

Working with the Ocean Bottom Seismic Team –

Personally, I think the phrase ‘Ocean Bottom’ sounds strange. It has connotations of treasure chests and weird glow in the dark fish with enormous teeth. Ocean Bottom Instruments sounds, if anything, even more strange, waterproof pianos?

What kind of people specialise in Ocean Bottom Instruments? One imagines a motley collection of socially inept scientists. Indeed they are scientists: hardworking, clever and enthusiastic about their field. They are ingenious people finding practical solutions to their everyday challenges. Their biggest challenge is getting equipment to work in salty water, at great depths and under great pressure. The equipment is expensive and needs checking and rechecking prior to being deployed to the bottom of the ocean. The OBS team are definitely NOT socially inept, they are witty, friendly and extremely patient with the Teacher at Sea. They are also physically strong: able to haul about large concrete blocks that even the most hench of gym types would think twice about before lifting. I have not yet met a ‘Sheldon’ on this expedition. That stereotype of a scientist is conspicuously absent from the RRS James Cook. I am working with a wide range peoples (mostly men – the subject of another blog), and of course everyone is different but everyone is lovely and everyone appears to love their work. Science – a wide and varied career, not one I considered as teenager (it never occurred to me that I could be a scientist) but a path I would certainly encourage today’s teenagers to think about. You don’t have to be super clever or super geeky, you just need to be enthusiastic about the field you are going into.

Ben and Nuno shifting HEAVY concrete in 24 degrees heat and 75% humidity – HENCH!!


I have had two days working with the Ocean Bottom Seismic team. I have been testing switches and placing batteries into radios and lights. Anna very kindly talked me through the procedure and it felt good to be doing a useful job.  These will be installed on top of the Ocean Bottom Instruments so that they can be located and picked up the RRS James Cook when they have finished their job on the bottom of the ocean floor and floated back to the surface.

Lights that will be beacons to aid collecting the OBS equipment.


I have also been tying ropes to the seismographs so that they can be hooked back on board when the ship gets close to them. Matt was extremely patient with me as the ropes needed to be very taut and this requires rather more strength than I possess. Mostly I provided an extra pair of hands – holding on to the rope so that Matt could tie it up.

The actual instruments (see picture) have a concrete base. The different components of the seismographs are within aluminium waterproof cylinders which are in turn in plastic tubes contained in yellow plastic crates. On top of the crate is a yellow hollow hard plastic buoyancy unit with glass balls inside (look up Archimedes for further information).

OBS equipment


The instruments will be deployed in a stratified manner -starting on Tuesday. The concrete base ensures that the instruments remain firmly stable and level at the bottom on the ocean. This results in accurate data being recorded on the seismographs devoid of distortion from oceanic currents.

There are finely engineered releases attached to each yellow plastic crate. These releases are fixed to the concrete bases which will stay on the sea floor. When the OBS team have collected all their data they send a signal to the acoustically triggered releases. A voltage is passed through a burn wire (the salt water provides a connection to the complete the circuit) which then dissolves and the spring loaded release bar drops enabling the seismographs to be released from their concrete blocks. The seismographs, along with their data, float back to the surface assisted by their buoyancy units, the lights and radios beacons give a precise location of each instrument.

Matt with a release (please turn your head 90 degrees – sorry)



Above – a release in situ

All in all there is approximately 2 million pounds worth of ocean bottom equipment being deployed once we reach our testing site. I look forward to telling you all about that in a few days time.

Any questions please do ask.


Angela 🙂

For more information see: obsatsea.wordpress.com



3 thoughts on “Working on board with OBS

    1. These are the floats. After the OBS is released from the concrete Base the equipment has to get back to the surface. Floats containing glass balls are used for this. Do look up Archemedes on Google for a better understanding of the principle.


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