In the small hours of Thursday morning, a ship docked in Newport, Ore.
Its cargo was sea water.
Its aim was to solve a mystery that has bedeviled scientists across the globe.
During the past month, a quiet corner of the ocean floor 150 miles off the Oregon Coast has been rocked with more than 600 earthquakes. Mostly small quakes, they’ve continued through Thursday with more than four of them topping 5.0 on the Richter scale – and the scientists still aren’t sure why.
But the water harvested from the ocean above the Juan de Fuca tectonic plate is an important clue. It might hold chemical information Oregon State University researchers at the Hatfield Marine Science Center in Newport can use to find out what’s causing the ‘quake-swarm’.
Amid all this uncertainty, University of Oregon professor of geology Gene Humphreys is confident that the quakes “aren’t a danger to anybody.”
“They’re not that large and they’re a long way away,” Humphreys said.
The strange thing about these quakes is that they’re in the middle of a plate, not on a fault line where plates meet and grind against each other, Humphreys said.
“They’re not going to lead to a large quake,” he said, because “a large quake needs a large fault.”
The quakes were first detected by underwater microphones, called SOund SUrveillance System hydrophones, formerly used to track submarine movement in the Pacific during the Cold War. But even when the Cold War ended, the hydrophones still couldn’t find peace and quiet. Scientists began using them to track whales, follow the movement of the tectonic plates and even hear hurricane wind from the surface.
In an entry on the Ridge 2000 tectonics blog, Robert Dziak, the OSU marine geologist leading the research, said “it is the first time in 17 years of SOSUS recordings that a set of earthquakes this focused and intense has occurred within the middle of the Juan de Fuca plate away from the major, regional tectonic boundaries … this situation represents a rare opportunity to learn more about this very unusual event.”
For millions of years the Juan de Fuca plate has plowed itself under the North American plate, giving birth to the Cascades. But the past month’s quakes have shaken the surface of the plate, about 44 miles north of the Blanco fault.
Separate plates compose the earth’s crust, and they float on an ocean of molten rock. They grind against each other along the lines separating them, called faults. This grinding can blast magma up through in the middle of a plate, which Humphreys said might be what’s causing the quakes.
“They aren’t a risk, and they don’t mean a large quake is coming, but they are scientifically interesting,” Humphreys said.
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