Cruise Blog by Frances Cooke: Day 1
July 7th, 2021
Text and photo: Frances Cooke (PhD Candidate in the Gas Hydrates and Free Gas Reservoirs research group at CAGE, working within the SEAMSTRESS project).
We departed Tromsø on the Helmer Hanssen before our first, of likely many, onboard fish lunches. We were glad of the sea breeze after the unusual Arctic summer heat during the past few days. The seas are calm which is always a relief knowing that your journey north is going to be a smooth one and we found the server machine room the perfect place to cool down! We are in transit returning to Vestnesa Ridge – West Svalbard to recover earthquake data from previously deployed ocean-bottom seismic instruments (OBS). OBS are instruments that contain seismometers and hydrophones that sit on the seafloor, listening and recording vibrations from shallow earthquakes.
Last view of the land: Vannøya
Onboard we have two of our colleagues from the Alfred Wegener Institute (Vera and Mechita), three from the Seamstress project (Andreia, Frances and Przemek) and two technical engineers (Stormer and Truls). We are busy setting up the GPS required for the active OBS experiment that will take place at the west of Vestnesa ridge. We have Sunil (in-house expert) present through video call while we are near shore! The setup ensures that we have precision in the timing and positioning of each shot fired during the active experiment.
Figures for planning of the active source experiment. The green filled circles (right) are 8 OBS deployment locations. The survey lines and circles are for the seismic planning.
Stormer and Andreia attach GPS antenna to railing
Last year during cruise CAGE20_5 we recovered 7 OBS as part of the Seamstress passive seismic experiment. This experiment took place between July 2019 and August 2020. The OBS instruments in the passive experiment record signals generated by earthquakes or other natural sound waves such as whale calls, instead of being actively generated by airguns. During the same cruise, we deployed 10 more OBS to begin a new experiment at the northern termination of the Knipovich mid-ocean ridge. We are now on our way back to recover them.
Figure from CAGE20_5 cruise report. Pink triangles are the OBS we are on our way to collect (North of the Knipovich mid ocean ridge – West Svalbard)
Read more about the SEAMSTRESS project here.