Research Cruise Investigates 'Lock Zone' Of Dangerous Offshore Fault

By Tom Banse

June 25-July 7, a research ship is retrieving dozens of seismometers that have spent the last year on the ocean floor off the Northwest coast. Earthquake scientists hope the data they're about to get will shed more light on the structure of the offshore Cascadia fault zone. That plate boundary will be the source of the Big One whenever it rips.

Ship-to-shore video shows how researchers are using a remotely guided submarine to pluck armored seismometers off the Pacific Ocean floor.

Sound from video: "Now coming into view is the TRM. TRM stands for trawl resistant mount..."

Crew members of the R/V Atlantis recover the submersible

Last summer, a different ship deployed these undersea instruments on the continental shelf and in deeper water. Sixty of them were scattered from Vancouver Island to northern California.
The undersea seismometers record tiny earthquakes that we can't feel on land. From that data scientists hope to extrapolate what's happening along our big offshore fault, the Cascadia Subduction Zone. We know the two crustal plates grinding against each other out there are stuck. In science-speak, they're "locked." 

University of Oregon geophysics professor Doug Toomey says a key objective of this investigation is to discover how widely tension is building up to a great earthquake.

Doug Toomey: "How large it might be and how damaging it might be depends to some extent on how large the lock zone is, in particular how far offshore and how far onshore it extends."
Crew members of the R/V Atlantis recover the submersible "Jason," after it connected a chain to an undersea seismometer off the coast of Oregon. By Matt Cooper, Univ. of Oregon.

Toomey expects the first scientific papers to interpret the data to come out later this year. (He leads what is called the Cascadia Initiative project. Toomey says the 40 to 50 million dollar effort is funded by National Science Foundation and includes a big chunk of federal economic stimulus money.) What's wrapping up now is the second of four planned cycles of undersea deployments and retrievals, each a year long.

Cascadia Initiative project:

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