Atlantis Probes Depths To Find Earthquake Epicenter

Daily Astorian | Aug. 2, 2013 5:06 a.m. | Updated: Aug. 2, 2013 12:06 p.m.

Contributed By:

EDWARD STRATTON

Astoria has a growing reputation as a stopover point for cruise ships, the iconic behemoths that periodically dwarf the Port of Astoria’s offices as their passengers swarm downtown.

Less noticeable are the research vessels and their academic passengers that periodically berth along Pier 1, gracing Astoria with some of the most advanced equipment and knowledgeable academics in the world.

One of those vessels, the research vessel Atlantis operated by Woods Hole Oceanographic Institution, departed Astoria Wednesday for a month-long cruise carrying mostly researchers from the University of Washington and three from Oregon State University.

They are running heat and fluid movement profiles 50 to 100 miles off the Washington coast, indirectly seeking an answer to one of the region’s most burning questions: Where could the next Cascadia Subduction Zone earthquake start?

Off the Pacific Northwest coastline between British Columbia and Northern California, the North American plate subducts the Juan De Fuca plate – an area commonly known as the Cascadia Subduction Zone. The big risk revolved around a magnitude-9 or greater earthquake emanating from the zone every several hundred years.

“There is a fault directly beneath Astoria, and that fault is ‘locked’ over a certain zone,” said Paul Johnson, one of the principal investigators on the expedition and an adjunct professor of earth and space scientists at the University of Washington.

The “locked” zone, said Johnson, is underneath the continential divide and controlled by temperature. The westward side of it, he added, averages 248 degrees Fahrenheit, while underneath Astoria and toward places like Seattle the temperature rises to 662 – in the middle is the “locked” zone.

“But we don’t know where that is. We don’t know if it’s far off sea. We don’t know if it’s deep inshore. When the fault gives and there’s a magnitude-9 earthquake, that’s where the epicenters are.”

The expedition, titled “Thermal Structure of the Cascadia Subduction Zone on the Washington Margin,” will use the remotely operated vehicle (ROV) Jason to measure heat and fluid flow data at 10 specific equally-spaced depth intervals along the margin, from 2900- to 500-meter depths. Johnson said there have been measurements showing particularly slow movement off the Washington coastline – the Atlantis is currently due west of the entrance to Willapa Bay.

Along on the expedition, funded by the National Science Foundation, are mostly instructors and graduate students from the University of Washington and OSU with projects related to its general goal.

Rick Berg, a graduate student of oceanography at the University of Washington, uses Mosquito fluid flow meters, its needles stuck into the seafloor by Jason. A dye is released through the needles, which is recorded by onboard pumps showing how fast it’s moving.

“That’s going to be really important for the heat flow guys,” said Berg, “because they’re going to be measuring mainly the heat flux out of the sediments. And to be able to get a temperature profile from that, you need to know what the fluid flow rates are.”

Rob Harris, an OSU geophysics professor on the cruise with one of his graduate students, brought his multi-penetration heat flow probe that looks deeper into the sub-sea floor sediments.

“It’s tethered to the ship, and it’s like a pogo probe,” he said. “We put it into the sediments, take a measurement after (20 minutes), pull it out, move the ship, do it again and in that way get a transect of the heat flow measurements.”

The data from the expedition, which ends in late August, will go public via the NSF’s GeoPRISM and University of Washington’s web sites within three months after the cruise. For more information on the expedition, visit http://tinyurl.com/thermalcruise

A floating research station

The Atlantis, owned by the U.S. Navy, is one of four vessels operated by Woods Hole.

“All winter and spring they’ve been refitting the vessel – it’s been in yard,” said 3rd Mate Amy Biddle. “Alvin was just done with a whole new interior. It’s redone every three or four years.”

The Atlantis, which employs about 20 operations staff and is built ready to accommodate new NSF-funded expeditions, started escorting scientific groups in May, taking the Cascadia Initiative Expedition Team from the University of Oregon out to deploy an array of seismometers on the seafloor to complement an array of stations onshore.

Its most recently completed expedition, which landed it back in Astoria after spending mid-July around the Juan De Fuca ridge, was led by principal investigator Andy Fisher, a professor from the University of California Santa Cruz who specializes in hydro geology. He led an expedition of several universities and separate institutions from California, Alaska, Hawaii and Maine studying the microbes, hydrology and geochemical makeup at the sea floor.

Fisher said his main focus was to “determine the qualities of the crust that allows the water to move.” The environments at the sea floor, he added, are very similar to early earth’s and what astronauts might encounter on other planets, a basic mix of heat, gas and water.

“We have NASA to go look at the worlds beyond us,” said Sharon Cooper, an education outreach specialist with Washington D.C.-based Consortium for Ocean Leadership, which represents research universities and went along on the trip. “But there’s still so much about our planet that we still don’t know.”

Cooper said part of the cruise was to gather data and retrieve and deploy equipment from and to what she calls “sub-sea floor observatories,” – known by Woods Hole as Circulation Obviation Retrofit Kits (CORKs) – more than 2,100 meters, or 1.3 miles, underwater. The observatories, which carry various instruments installed by ROVs such as Jason, top holes drilled about 1,600 meters into the earth’s crust.

There was a heavy educational component, said Cooper, with teachers onboard to develop curriculum, live feeds showing Jason’s and Atlantis’ exploits and informational videos created underway and available at http://explorationnow.org/atlantis/

The current expedition ends late this month, after which Biddle said the Atlantis heads down to start Alvin’s first sea trials off the coast of California. The Atlantis is specially outfitted as the delivery vehicle in the U.S. scientific fleet for the manned submersible.

“This time they took it completely apart, made a whole new sphere for it that goes deeper and then put it all back together,” said Biddle about the new titanium observatory on Alvin, which includes its own operations crew of about six and holds two scientists and a pilot.

Since its inception in 1964 as one of the world’s first deep-sea submersibles, Alvin has made more than 4,400 dives and can reach more than half of the world’s sea floor. Among its more notable exploits were the discovery of a lost U.S. hydrogen bomb off in the Mediterranean in 1966, exploring the first known hydrothermal vent sites in the 1970s, and surveying the wreck of RMS Titanic in 1986.

This story originally appeared in Daily Astorian.

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