Updated: 7 Small Quakes off Oregon Coast; Tsunami Survival Tips

Published 06/01/2015 at 6:31 PM PDT - Updated 06/02/2015 at 6:20 AM PDT
By Oregon Coast Beach Connection staff

(Oregon Coast) – Seven shallow earthquakes caused a bit of shake, rattle and roll beneath the waves off the Oregon coast in just a little over 24 hours, but they were not of sufficient size to create a tsunami and barely large enough to be felt onshore.

They were centered a little less than 300 miles west of Newport, clocking in between 5.9 down to a 4.2 magnitude. The first hit at 11:52 p.m., with three smaller aftershocks after that. The highest, a magnitude 5.9, occurred Monday at 1:11 p.m. Two others occurred after that.

All five occurred about six miles beneath the ocean floor, which the USGS said is fairly typical of this area. This is the spot where the Juan de Fuca plate is slowly separating from the Pacific Plate, causing small quakes to happen with regularity. The USGS said this is nothing new, nor is it a precursor to something larger. These quake clusters happen occasionally and they are harmless. The USGS said it takes a 7.0 quake to create a tsunami.

In fact, they are predicting more smaller aftershocks in the coming hours and days. Often, these larger events are followed by dozens of smaller quakes. You can keep track of these in real time at the Oregon Coast Live Earthquake Tsunami page.

However, these fault lines will one day create a massive earthquake, likely in the magnitude 9 range, say scientists. That is the same magnitude that hit Japan in March 2011, and it is expected to create a devastating tsunami for the Oregon coast. Scientists say such a quake off this shoreline will be felt not just throughout Oregon but in Washington, California, Idaho and even Montana.

The last such quake happened off the Oregon coast in 1700, corresponding with records of a tsunami hitting Japan. Scientists say this coastline has received one of these larger quakes about every 300 – 500 years.

Oregon officials are quick to remind the public what to do in case of an earthquake on the Oregon coast, saying “know your tsunami escape route.”

Ali Ryan, earth science information officer for the Oregon Department of Geology and
Mineral Industries (DOGAMI), said if an earthquake hits while you're on the beach, a tsunami is right behind. You likely have as little as 15 minutes to make it to higher ground.

Ryan said as soon as the ground stops shaking, you need to bolt for a spot as high as possible above the waves.

“You’ll get to an assembly area much faster if you’re already familiar with the evacuation route,” Ryan said.

Using roads will likely be impossible, so you'll have to be prepared to go on foot. Take note of the tsunami evacuation signs along the coast towns. This is particularly important in towns like Seaside or Cannon Beach, where about 75 percent of the attractions and businesses are in the tsunami zone.

“Incorporating the route into a regular exercise routine or exploring a different route on
every visit to the coast is a good way to get to know those paths to higher ground,” Ryan said.

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