Check out the video blog being produced by students aboard CIET leg 3! Subscribe to Richard Allen’s YouTube Channel or follow @BerkeleySeismo on Twitter for new episodes.
Dr. Robert Dziak contributed this cruise summary:
“The OBS deployment cruise was an unqualified success. Our
highly efficient team of sea going professionals was able to maintain a
brisk deployment schedule and completed all 25 ocean bottom seismometer
deployments within 8 days. We averaged 3 deployments a day, including
time for instrument surveys to derive their precise locations. The only
thing that suffered was our sleeping habits, but it was well worth it!
We also wish to express our gratitude to the Captain, crew, and Marine
Tech of the Wecoma for their hard work that allowed our project to be
“All 25 SIO and LDEO instruments were deployed with sites prioritized
prior to the cruise in consultation with the community to focus on
different scientific questions. This prioritized sequence was further
modified prior to the cruise to accommodate recommendations from the
Oregon Fishermen’s Cable Committee (OFCC), The Oregon Trawlers
Association, the Quilete and Quinault tribes, and the Canadian Trawlers
Association, all of which represents the various fishing communities on
the Oregon, Washington and Canadian continental margins. Of the 25
instruments deployed, one SIO Abalone instrument lost its anchor as it
was being deployed. Another Abalone was deployed in its place as a spare
anchor was sent to Newport during the cruise. We returned to port
briefly after deploying the first 24 instruments, and returned to the
site to deploy the lone remaining Abalone. All instruments will remain
on the seafloor until the summer of 2012.”
We have traveled north to test two Cascadia seismometers that were deployed earlier during the first leg during July. A specific frequency of sound (between 9 and 13 kilohertz) is sent down to check if the instrument package is working. Sometimes a fishing trawl can flip over the seismometer, rending it useless. If the instrument is working, it responds with a series of audio chirps that are picked up here on the Wecoma.
So far we have deployed five Cascadia and four Abalone seismometers. Another five are scheduled for deployment through the night.
Yesterday, we deployed three seismometers, two “Abalones” from Scripps Institute of Oceanography with the trawl resistant design and one from the Lamont-Doherty Earth Observatory (LDEO) called “Cascadian” which also has an absolute pressure gauge and hydrophone. These seismometers are generally deployed deeper along the continental margin.
There are two sets of Ocean Bottom Seismometers (OBS), 10 were built by Lamont-Doherty Earth Observatory (LDEO) and include pressure gauges. The pressure gauges are for sensing vertical seafloor uplift and will be deployed on the edge of the continental margin to detect strain accumulation between the North American and Juan de Fuca plates. The remaining 15 OBS were built by Scripps Institute of Oceanography and are designed to be trawl resistant. Called “Abalones” they are pyramidal shaped and can be deployed from 100 m to 6000 meters depth.