On July 2, we finished deploying over twenty ocean-bottom seismometers as a part of our marine expedition to study a major tectonic boundary offshore Alaska. Ocean bottom seismometers (OBS’s) are autonomous instruments that sit on the seafloor and record sound waves traveling through the earth and the water. Floats made from glass balls and syntactic foam make each OBS buoyant, but an anchor holds it on the seafloor during the study. We communicate with each OBS acoustically, allowing us to send it a command to release from its anchor when we are ready to recover it.
For our project, we are placing OBS’s from Scripps Institution of Oceanography on the seafloor along two lines that span the major offshore fault zone. Immediately prior to deployment, we assemble the main components of each OBS on deck while the ship transits between sites. When we arrive at the deployment site, the ship slows down, and the OBS is lifted over the side of the vessel and into the water with a large crane. We release it, and it sinks to the sea floor. Thanks to the skill and hard work of the Scripps OBS team and the ship’s crew, we were able to deploy one OBS every hour, which is very efficient!