Category Archives: 2011 Crew

Cruise Summary

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.”

Last Day at Sea

We deployed the 24th seismometer at 9: this morning. The atmospheric pressure is dropping and the seas are rising, making the deployments more challenging. The roll of the ship increases the difficulty of both getting the seismometer to the rail and successfully releasing it over the side. We are heading back to Newport to pick up another anchor plate for one that we lost a couple of days ago. We’ll be doing a “touch and go”, without even putting out the gangplank. Fortunately, the last site is close to Newport.

At 9:50, seven of us met in the wheelhouse for a live Skype broadcast to HMSC. Tracy Crews organized “Career Day” for high school students and we responded via two way video to student questions from the Hennings Auditorium. Our virtual presence was projected on its large screen.

Bob Dziak – Chief Scientist – Professor, Marine Geophysics, OSU,  – What are you studying out there? What’s it like working at sea?

Dave Ogorman – Marine Instrumentation Engineer, Wecoma – How did you choose this career?

David Gassier – Ocean Research Engineer, Lamont-Doherty Earth Observatory, Columbia University – What is your background? Is there a specialized degree in Ocean Engineering?

Del Bohenstiehl – Co-chief Scientist – Associate Professor – North Carolina State University – What do you like most about being a scientist?

Matt Fowler – Mooring and Instrumentation Engineer – Research Assistant, OSU – What is your background? What do you enjoy most about your job?

Martin Rapa – Development Engineer, Scripps Institute of Oceanography – What did you have to consider when designing an underwater seismometer?


Tag lines are used to stablize the deployment


Matt is struggling with a jammed quick release mechanism

CTD Cast

CTD stands for conductivity, temperature and depth. These terms refer to the changing seawater characteristics that the CTD array encounters as it descends. It electrically sends continuous measurements back to the ship.

Conductivity is an electrical measurement of salinity. The salinity varies near the surface, but is a reliable 34 to 35 parts per thousand for most of the descent. The seawater temperature drops to about 3 degrees Celsius, about 37 degrees Fahrenheit.

We dropped the cabled CTD to just above the seafloor depth of 1500 meters (4921 feet). The pressure increases about one atmosphere for every 10 meters (or ~33 feet) of depth. We attached to the CTD array two nylon bags filled with Styrofoam cups, decorated by students from the Lincoln County School District. When subjected to pressure 150 times greater than standard atmospheric, the air is squeezed out from the Styrofoam.

Second Day at Sea

The Abalones are in the foreground; the Cascadians are lined up in the back.

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.


Ocean Bottom Seismometers

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.