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Mon June 4, 2012
Cruising the coast for signs of where 'the big one' will hit
One of the world’s most advanced research ships will be cruising along the Washington and Oregon coasts this month – to look for clues about giant earthquakes.
A zone that runs parallel to the coast – but deep beneath the sea – is known to have unleashed mega-quakes in the past, similar to the one that caused the giant tsunami last year in Japan. The Cascadia fault zone runs about 700 miles alongside Vancouver Island, Washington and Oregon.
There's physical evidence for a massive earthquake in 1700. But the impact from the next big one probably won't be uniform along the entire coast, and it would be nice to have a bit more detail, says Ken Creager an earthquake scientist at the University of Washington. He's trying to figure out where the strongest shaking and worst damage will happen when that big fault lets loose.
"Are there patches along the fault which are perhaps stronger and get stuck for longer periods of time, and then when the big earthquake happens will have a lot stronger shaking?"
Creager's not involved with the ship, but he’s excited to see the results from this summer's cruise.
Ship can see below the surface
The ship, named the R/V Langseth, comes from Columbia University and it specializes in making 3-D maps of rock and soil formations that are impossible to see, such as tectonic plates and magma chambers. It uses sound-waves that can be recorded by seismometers on the ship and on-shore.
"It's the primary method available to scientists to 'see' beneath the seafloor -- to construct detailed images of the sediments and Earth's crust that lie beneath the seafloor -- analagous to x-rays," says lead scientist Suzanne Carbotte, of Columbia's Lamont-Doherty Earth Observatory, in an email.
The ship also will measure how much moisture is getting sucked into the earth at the off-shore fault-line.
"That might explain ... why we have volcanoes where we do, or the biggest we've had in the Seattle area have been near where Nisqually earthquake was, near Tacoma, but very few large earthquakes hit Oregon," says Creager.
Focus on Washington's coast
The mapping project builds on a recent national focus on the fault zone off Washington's and Oregon's coast. The National Science Foundation launched the "Cascadia Initiative" with federal stimulus money in 2010. Researchers are installing new sensors to better understand the fault and its risks, including 60 sensors on the ocean floor.
The ship won’t be visible much from shore, although it will come close to Grays Harbor in mid-June. It sets sail from Astoria on June 11th, and will spend a month sailing back and forth in straight lines, while seismometers listen intently for its sound-waves.