A cluster of 14 mostly magnitude 2 earthquakes murmured in the ocean off the coast of Oregon between Brookings and Gold Beach this past week.
The most recent – and closest – was a 2.9 magnitude quake reported 26 miles off Brookings and 22 miles off Gold Beach on Thursday. The cluster of quakes that rattled here last week were mostly in the 2.0 magnitude range, except for one 4.0 tremor Sunday about midway up the coast.
Most people didn’t notice. The sheriff’s office cancelled it regular tsunami siren test the day of the 4 earthquake so as to avoid confusion. Local disaster preparedness officials didn’t give it much thought. The National Oceanic and Atmospheric Association issued no tsunami alerts for the area.
Yet the flurry came during the same week a new study was released saying Oregon is due for a major seismic event, sometime in the next 50 years.
If the two are related is anyone’s guess, said Chris Goldfinger, an Oregon State University marine geology professor and author of the study.
Yet, the 184-page report carries a lot of weight among geologists.
The study says there is a 40 percent chance of an 8.1 to 8.3 magnitude quake occurring between Florence and Cape Mendocino, Calif., in the next 50 years. The chances of a larger one, say 9.0 and above, are only 10 percent, but such a quake could affect the entire coastline.
“Normally, the Cascadia Subduction Zone is very, very quiet,” Goldfinger said. “Chatter I’ve heard among seismologists, they think they’re pretty deep in the Juan de Fuca slab. But no one would stick their neck out and say what they think they mean.”
Local emergency preparedness experts aren’t overly concerned about the local quakes, either, said Don Kendall, county emergency preparedness director.
“We just know we’re ready; it’s time,” he said. “We’ve been going along with nothing really happening for a really long time period.”
Earthquake science – particularly prediction – is still in its infancy.
Some scientists are trying to determine if a series of small earthquakes, like the ones experienced this week, is an omen for a monster quake, or if they merely released some of the pressure that constantly builds up along fault lines.
Goldfinger was in Japan when the 9 magnitude earthquake struck March 11, 2011.
“There was a 7.4 before the 9,” he said. “They have an earthquake that size every 10 years or so, so they’re used to them. But after the big one, it (the smaller shock) turned out to be a ‘foreshock.’ Ahead of time no one can say.”
The last major “megathrust” earthquake – a seismic event of 9 magnitude or larger – to strike the northwest coast was on Jan. 26, 1700. That precise date was determined by searching Japanese weather records that show a tsunami totaled a barge on that date. The earthquake that caused the tsunami is believed to have originated along the Cascadia Fault.
Based on that and data from other earthquake zones in the so-called Ring of Fire lining the Pacific Ocean, another should hit within the next 50 years.
“It’s different for each fault,” Kendall said. “You’ve got two trains of thought. On one side, perhaps they’ve been (occurring) like that for awhile but now we’re more sensitive to it because of the fear factor. On the other side, maybe it could be a prelude (to a megathrust quake). Or it could be anything in between.”
Because earthquake prediction is virtually impossible – and each tremblor is different – people need to have ingrained in their minds what they need to do when one hits.
Kendall, because of the nature of his job, is supposed to be alerted by cell phone every time an earthquake of 2.5 or larger hits, primarily in case one is large enough to create a tsunami. An earthquake in southern Oregon might be horrific, but a resulting tsunami would be disastrous.
The local quakes last week didn’t trigger an alert.
“I receive alerts two to five times a day from all around the Ring of Fire,” he said. “A 5.6 would generate a tsunami. We see them in Alaska in the 5 region every other day.”
Kendall doesn’t even think about rumbles unless one hits 5 or higher.
“I’m from the Bay Area; I’m kind of desensitized unless it’s a 5 or bigger. A 7.2 that hit the Bay Area … I’ve been through that.”
Instead, he’s all about preparedness.
“What are you going to do? Go to your neighbor’s, break in, eat all his food and get into a fight? Is the government going to help? Well, that’s fine and dandy, but who’s really going to get those needed supplies? The high-population areas. One person alone means absolutely nothing. It’s battlefield triage.”
He has emergency kits at his home, in his car, at his office.
“So, I’m at work, I think, ‘Where do I go when it hits now?’” he said. “Tonight, I’m at home, ‘Where do I go when I’m at home? How are my wife and I are going to get through this?’
“On the other hand, if I stood around and worried about it, I’d be frozen like a deer in the headlights. It may not happen this second – I haven’t gone so far to wear a Bat belt – but I know where my kits are.”
That’s not that he makes light of the situation.
“Every earthquake is significant,” Kendall said. “So many of them are of this small nature. You can’t freeze like a deer every time there’s a tremblor.”
“If we have a great earthquake in the next week, I’ll tell you the significance (of the cluster of quakes last week),” Goldfinger said. “Then, they will have been foreshocks. No one can say.”