Calling OBS home before the weather

Luan nabs a returning WHOI OBS
Yesterday, we finished recovering 29 ocean bottom seismometers deployed along the Emperor Seamount Chain, thus completing our field program in the Emperor Seamount Chain.  We were blessed with a long period of excellent weather for collecting data on the 15-km-long seismic streamer and for most of the OBS recoveries.  Good weather is particularly important for the latter.  Despite all of the technology that enables us to put a seismometer on the seafloor in water depths of 6300 m (~19,000 ft!) and send them commands to come back to the ocean surface, our method of fetching them from the ocean onto the ship is quite basic, but still impressive! The ship’s mates drive this large vessel right up next to the floating OBS, and people reach out and hook the OBS from the starboard deck using a long stick!  We then use a crane to hoist them out of the water.  This procedure becomes much more difficult in rough weather. Maneuvering the vessel is more challenging when the winds and waves pick up, and deck operations to recover the OBS are also harder if water is coming over the side and ship is rolling.  As we finished creating sound sources to be recorded by the OBS and started picking them up, the forecast began to show some nasty weather in our area near the end of our OBS pickups.  We thus hastened the pace!  We cut off the final part of our seismic source line to start pickups early, and then everyone did an amazingly efficient job of getting the OBS’s onboard. We finished last night at ~9 pm local time, way ahead of schedule and just as the weather was starting to go downhill.   

Donna Shillington
LDEO


GEOMAR OBS lifted up and onto the deck



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