Here’s what seismologists are saying about the flurry of Northwest earthquakes
Five moderate to strong earthquakes Monday at the northern end of the Cascadia Subduction Zone fault don’t have seismologists too worried.
But the series of earthquakes, off the northern tip of Vancouver Island in British Columbia about 350 miles northwest of Bellingham, did raise some eyebrows, said Paul Bodin, manager of the Pacific Northwest Seismic Network at the University of Washington.
“In the scheme of things, these aren’t big quakes. But that much activity in our neighborhood does make you think,” Bodin told The Bellingham Herald.
Bodin said it wasn’t known if the quakes were precursors to a larger event.
“There’s no sign that it might be a harbinger. I don’t think that these were abnormal, outside the normal fluctuations of seismicity. When an area’s been quiet for a while and it kicks up like this — we pay attention,” he said.
All five quakes were in virtually the same location and are considered “moderate” and “strong” in magnitude.
Monday’s first quake registered 5.2 on seismographs at 8:44 a.m. PST, followed by a second temblor of 5.6 magnitude at 11:13 a.m. The third quake was at 11:50 a.m. and had a preliminary magnitude of 6.0, followed by a fourth quake at 12:56 p.m., also a 6.0. A fifth quake was at 3:38 p.m. with a magnitude of 4.7.
No damage or injuries were reported because they were in a sparsely populated region.
A quake of magnitude 5.0 to 5.9 can move heavy furniture and cause slight damage to buildings, according to the U.S. Geological Survey and the website UPSeis at Michigan Tech University.
Only about 500 such quakes occur worldwide every year, UPSeis said at its website.
A quake of magnitude 6 can cause heavy damage to nearby populated areas. Only 100 such quakes occur each year worldwide.
NOAA’s Tsunami Warning System said that a tsunami wasn’t expected from any of the five quakes.
Bodin said the quakes were too small to generate serious wave action, and, in any case, they were “strike-slip” events where the ocean floor moves side to side rather than up and down.
But the Cascadia Subduction Zone fault where the quakes occurred is capable of producing quakes up to magnitude 9, which would spawn a deadly tsunami and shaking that would rock the Northwest, according to a 2015 New Yorker article that sparked concern among the public and emergency-response officials.
“(Monday’s quakes were) like many earthquakes that have been there in the past,” Bodin said. “That’s a handful of earthquakes, and it certainly merits keeping our eyes on it.”
This story was originally published December 24, 2019 at 11:45 AM.
