Small earthquake jolts parts of Clark County


The 2.9 magnitude quake hit Thursday afternoon northeast of Yacolt in the Gifford Pinchot National Forest

BATTLE GROUND — A 2.9 magnitude earthquake jolted part of northeast Clark County on Thursday afternoon.

The quake hit at 12:49 p.m., around 17 miles north-northeast of Yacolt, and 25 miles north-northeast of Battle Ground.

A seismographic representation of a 2.9 magnitude earthquake that hit east of Amboy on Thursday. Image courtesy US Geological Survey
A seismographic representation of a 2.9 magnitude earthquake that hit east of Amboy on Thursday. Image courtesy US Geological Survey

People who felt the quake described it as a short, sharp jolt that rattled dishes in the cupboards.

Paul Bodin, a research professor at the University of Washington in Seattle and manager of the Pacific Northwest Seismic Network said they received more than two dozen reports from people who felt the quake, mostly from northeast Vancouver up through Yacolt and Amboy.

“A magnitude three earthquake just takes a second or two slip on the fault,” Bodin told Clark County Today. “They don’t drag on for a long time of intense shaking.”

The quake, which was determined to be around six miles deep, was in the Gifford Pinchot National Forest, in an area known as the Saint Helens Seismic Zone.

“It’s an interesting zone of earthquakes,” Bodin says. “There’s a branch of the Saint Helens seismic zone that goes to the northwest, up toward Morton. And then there’s a branch that goes down to the southeast.”

A quake intensity map shows Thursday’s 2.9 magnitude trembler east of Amboy didn’t make much of an impact. Image courtesy US Geological Survey
A quake intensity map shows Thursday’s 2.9 magnitude trembler east of Amboy didn’t make much of an impact. Image courtesy US Geological Survey

While the quake was centered in the area recently burned by the Big Hollow wildfire, Bodin says there’s no reason to believe the fire was connected to the earthquake. While landslides can happen in areas recently burned, and sometimes register on sensitive seismic equipment, those waveforms are easily distinguishable from those of a typical quake.

And earthquakes are typical for that area of Southwest Washington.

Data from the US Geological Survey (USGS) shows dozens of small earthquakes on and around this area, most of them centered directly above the sleeping volcano.

It’s a sign, Bodin says, that the volcano likely won’t sleep forever, but not an indication of any imminent activity.

“These usually tend to be a one off in this seismic zone,” says Bodin. “There tend to be isolated earthquakes like this.”

As of Thursday afternoon, Bodin says their equipment had not detected any aftershocks from the small quake.

“There is a small chance that this could be followed by an earthquake of the same size or larger,” he says, “but that chance is really, really, really tiny.”

This graphic shows where the Cascadia Subduction Zone is off the Pacific coast. The fault is expected to cause a major earthquake at some point in the near future. Image courtesy State of Oregon Department of Emergency Management
This graphic shows where the Cascadia Subduction Zone is off the Pacific coast. The fault is expected to cause a major earthquake at some point in the near future. Image courtesy State of Oregon Department of Emergency Management

It’s also not necessarily a sign of anything going on with the Cascadia Subduction Zone, where the Juan de Fuca tectonic plate buckles under the North American plate and is expected to eventually cause a massive quake known as ‘The Big One.’

“This was a tectonic earthquake,” Bodin explains. “It was a slip on a vertical fault, where one slid sideways past the other, not up or down.”

While scientists continue to learn much more about how tectonic plates, volcanoes, and subduction zones interact, it’s generally believed that small quakes on or around Saint Helens are likely to be isolated incidents, and not a sign of some greater seismic activity in the offing.

Still, every jolt or tremor offers up a reminder, Bodin says, that we live in a seismically active area and “should always be as prepared as possible.”

“I don’t think this is going to be the crowning glory problem of 2020, let’s put it that way,” he added.

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About The Author

Chris Brown comes to Clark County Today with 15 years of local news experience as a reporter, editor, and anchor at KXL News Radio and KOIN-6 TV in Portland. In 2016, he won an Oregon Association of Broadcaster's award for Best Investigative Reporting for a series on America's Violent Youth. He has also been awarded by the Associated Press for Best Breaking News coverage as editor of Portland's Morning News following the 2015 school shooting at Umpqua Community College in Roseburg, Oregon. The second oldest of eight home-schooled children, Brown graduated from high school two years early. After several odd jobs, he earned an internship at KXL Radio, eventually working his way into a full-time job. Brown has lived in Clark County his entire life, and is very excited at the opportunity to now focus full-time on the significant stories happening in his own back yard, rather than across “the river.’’ After a few years in Vancouver, he recently moved back to Battle Ground with his wife and two young daughters. When he's not working to report what's happening in Clark County, Brown enjoys spending time with his family, playing music, taking pictures, or working in the yard. He also actually does enjoy long walks on the beach, and sunsets.

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