We started the cruise being responsible with the law of the sea (we assisted a smaller ship that was in trouble). Luckily for the crew of the small ship and for ourselves, the weather was nice and the sea calm. So we collected the 7 seismometers (5 from Geomar, 2 from UiT) that were at the bottom since last year and started the next part of the experiment.
7 Ocean bottom seismometers from the Alfred Wegener Institute (AWI) waiting to go overboard. Photo by Andreia Plaza-Faverola
This time we left 10 seismometers at the bottom, 8 from AWI and 2 from UiT, distributed in a faulted region north of the Knipovich Ridge. In average the deployment of each instrument took about an hour. This included a test of the releasers (those we talked about in the first post of the expedition). The releasers were sent down to 2000 m inside a cage to check whether they were receiving the signal from the ship and responding with the task they were asked to do (open the hook!, close the hook!, send a signal back to the ship!, etc). Some of the releasers failed to obey in the last minute, almost like a child who refuses to do this and that. So they needed to be replaced (the releasers…). It was a long couple of days for all, in particular for those preparing the instruments to be thrown overboard.
Henning (AWI) observes and ensures the OBS is carefully driven to the sea surface by the crew member that operates the crane. Photo by Andreia Plaza-Faverola
Placing the instruments at sea went smooth. Now we all wait until next year to recover the instruments and hope they recorded small earthquakes originated or somehow related to faults that show up at the seafloor (along the so called passive continental margin) and that may be related to the opening of the Knipovich mid-Ocean ridge. Since shallow seismicity is not expected in the zone where the instruments sit (again, it is considered a “passive” continental margin slope), we can say in other words, we hope the instruments record something unexpected…
Towards the end the whales were still with us.
From left to right: an instrument, the crew and a whale. Photo by Vera Schlindwein
Text by Andreia Plaza-Faverola
Photos by Vera Schlindwein and Andreia Plaza-Faverola