Andy Matarrese, Columbian
environment and transportation reporter
Published: November 12, 2015, 6:35pm
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Dozens of people reported feeling a small earthquake in Clark County’s Felida area Thursday morning, according to the U.S. Geological Survey.
The 2.8-magnitude tremor occurred around 8:15 a.m. near Frenchman’s Bar Regional Park between Vancouver Lake and the Columbia River. Clark County emergency dispatch personnel said that there were no reports of damage or injury associated with the quake.
Though it didn’t cause much of a ruckus, the quake did prompt 74 people in Oregon and Washington to log onto the USGS “Did you feel it?” website (pnsn.org/earthquakes/recent) to report whether they had. Most respondents reported feeling a weak shake.
The quake, with a depth of 12.93 miles, fell within a magnitude range that’s strong enough to be felt but easy to miss — between the magnitudes of 2.5 and 3.5 — experts with Pacific Northwest Seismic Network in Seattle have said.
It’s relatively common for small quakes to spring from microfaults that crisscross the entire region, and this is far from the first time the area has felt a small quake.
John Vidale, the director for the Pacific Northwest Seismic Network, said there have been about 120 quakes of magnitude 2 or greater around the Portland-Vancouver metro area in the past 25 years.
“This one today was near a cluster of events that happen fairly frequently,” he said. “This is sort of in the range that we expect every year in that region.”
In June, a 3.2-magnitude earthquake was reported in northwest Oregon. In December 2014, a 2.7-magnitude temblor was measured near Vancouver Lake.
In January 2013, a magnitude-3.7 earthquake centered near Amboy was widely felt in the Portland-Vancouver area. On Valentine’s Day in 2011, a magnitude-4.3 earthquake shook near Mount St. Helens.
Even the 2011 quake is nothing compared to the catastrophic earthquake that scientists expect to be unleashed by the Cascadia Subduction Zone fault someday. “The big one” could be a magnitude-9.0 monster that causes widespread damage across the region, experts say. The Cascadia fault sits off the coast, and stretches from Vancouver Island in Canada to California.
System tested
Vidale said Thursday morning’s shaking was another opportunity for the network to test its early warning system.
“It’s running in kind of a test phase at the moment,” he said.
The early warning system received an additional $5 million in federal funding this summer to upgrade seismic stations and help develop an earthquake alert system that would give people notice seconds to minutes before the ground shakes.
Vidale said he and his colleagues got word of the quake within 9 seconds, and the readings were accurate as far as its strength.
“It was right on in this case,” he said.
With all the planned instruments installed, the notice would have been cut down to 3 seconds, he said.
Earthquake experts say even seconds’ notice can make a difference in preserving infrastructure or giving people time to take cover.
Small events like Thursday’s help the system’s designers test the software and review the accuracy of their data, Vidale said.
“Really just making sure the system works end-to-end,” he said.
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