6 November 2013, Karin Sigloch
We have fallen behind on blogging during a very busy week. As we are nearing the end of Leg 1 of the cruise, we have recovered 26 ocean-bottom seismometers. So far, every instrument has responded to our calls and returned from the seafloor – the most basic measure of success. Most instruments have done their job, but not all. A few have returned without data, or only hydrophone data, and some have drained their batteries prematurely. We are sorting through large quantities of recorded time series and engineering log files, trying to understand what we have obtained in each case, and why.
Compared to the variety of complications encountered in data logging and seismometer hardware, OBS recovery operations have been quite smooth. We found that the rise time of an OBS, typically 50-70 minutes depending on depth, can be predicted to within one or two minutes. Even better, the Meteor was recently equipped with a directional radio receiver that has so far detected every surfaced OBS by its emitted radio signals – often long before our handheld radio device or eyes could have. Compared to tales of heroic search attempts in the dark ages, it has become almost too easy – but such is progress, and we love the goniometer’s beep that heralds the arrival of yet another seismometer.
While the Meteor’s officers and skilled deck crew have perfected their techniques for getting the instruments on board, some of us have perfected their documentation skills. The two photos are extracts from an underwater movie of a recent recovery.
RR04 has been approached and is floating in on the starboard side of the Meteor, in an absolutely calm sea – “duck pond weather”.
Seconds before it is pulled out of the ocean by the ship’s crane, RR04 has to roll around – a moment captured by Guilhem’s underwater camera strapped to a long sailor’s rod.