The two main components necessary for seismic reflection data collection are the air guns and the streamer. The air gun array on the ship contains compressed air (a total of 6600 in3) which is fired off at about 2000 psi. The airguns fire at a set distance interval (either 37.5 and 50 meters for this cruise), which can be adjusted for each line, if needed. The energy from the air guns then travels through the water column, and reflects off the seafloor, or continues through the boundary and reflects off a different layer in the subsurface. These reflections travel back through the layers they penetrated, and through the water column once again. This is where the streamer comes into play. The streamer uses groups of hydrophones in spatial intervals to detect the reflected energy. Hydrophones contain piezoelectric crystals, which detect changes in pressure. The groups of hydrophones detect the signal, then average it for the group, and send it back to the computers on board the ship. There are 1212 channels detecting pressure changes, and the streamer is 15 kilometers (about 9.3 miles) long.

The air gun arrays and streamer can be set to the desired depth (currently 9 and 10 meters, respectively). The air guns are kept afloat by buoys on the surface, and their depth is determined by ropes and metal chains that connect them to the buoys. The streamer is kept afloat with foam inside the tube, and with depth-controlling devices placed periodically on the streamer, called birds. The birds are used to adjust the depth of the streamer while it is in the water, and have wings that are controlled by the onboard computing system and can be directed to move the streamer up and down.  If a big ship is about the steam over the streamer, the birds can be directed to dive.

 

 

 

 

 

 

 

 

 

— Kelly Olsen and Brooklyn Gose

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2 thoughts on “The Gear

  1. Wishing all the best to Science Party (several I have had the honor of sailing with before) and to my old Technical Crew Friends there on board as well. Hope all goes without a hitch, good weather, and safe sailing and loads and loads of Great data to take home with you!
    cheers,
    Mike Martello

    Reply
  2. Hi Mike, We are thrilled to see that someone out there is watching the blog. Your old friends here all say hi. The cruise so far has been going well – 15-km long streamer; many terabytes of data; everyone happy and healthy at the 1/2-way point. Anne

    Reply

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