Earthquake News

UW scientists make a discovery that helps them comprehend the earthquake hazard

A team of scientists from the University of Washington has made a remarkable discovery during a research cruise aboard a vessel off the coast of Oregon. While the team was dealing with a weather-related delay, the ship's sonar detected unexpected plumes of bubbles about three-quarters of a mile below the ocean's surface. An underwater robot was deployed to investigate the source of the bubbles, revealing that they were just a minor component of warm, chemically distinct fluid gushing from the seafloor sediment.

The unique underwater spring, named Pythia's Oasis by the scientists, is believed to be sourced from water 2.5 miles beneath the seafloor at the plate boundary. The fluid regulates stress on the offshore fault and is found near vertical faults where the oceanic and continental plates meet. This is the first known site of its kind, and similar fluid seep sites may exist nearby, although they are hard to detect from the ocean's surface.

The Cascadia Subduction Zone is a major earthquake concern for scientists, as it includes a "megathrust" fault that stretches from Northern Vancouver Island to Cape Mendocino, California. The fault separates the Juan de Fuca and North American plates, with the Juan de Fuca plate being pushed under the North American plate. Up to depths of 19 feet, the Cascadia zone is locked, while stress builds up until the fault's frictional strength is exceeded, and a massive earthquake occurs.

The newly discovered fluid leak is located approximately 50 miles offshore from Newport, Oregon. The fluid acts as a lubricant on the fault and ratchets up the friction between the plates. "The megathrust fault zone is like an air hockey table," explained Evan Solomon, UW associate professor of oceanography. "If the fluid pressure is high, it's like the air is turned on, meaning there's less friction, and the two plates can slip. If the fluid pressure is lower, the two plates will lock – that's when stress can build up."

The fluid release from the fault zone is like a leaking lubricant, said Solomon. That's bad news as less lubricant means stress can build, creating a more potentially damaging quake. According to the study published in the journal Science Advances, the fluid is coming straight from the Cascadia megathrust, where temperatures are estimated at between 300 to 500 degrees Fahrenheit. A significant fluid leak off central Oregon could explain why the northern portion of the Cascadia Subduction Zone, off the coast of Washington, is believed to be more strongly locked, or coupled, than the southern section off the coast of Oregon.

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