A funny thing happened on my way to doing the 5 o’clock weather forecast: an earthquake hit a single mile northeast of Amboy, Washington and was felt as far away as Vernonia in the Coast Range, Sherwood on the metro area’s west side and Oregon City on the metro area’s east side.
I sure didn’t see that one coming at 5:03pm! I doubt you did, either.
But maybe you felt it. There are some great posts on my facebook weather page about what people felt and heard during the southwest Washington earthquake.
First report, it was a 3.5, then geologists revised it to a 3.6–and moments later a 3.7 magnitude quake. Revisions are common. The shallow quake estimated to be 5.5 miles deep at first was actually even shallower once geologists reviewed it. A mere 4.7 miles down. Compare that with the quakes under the Pacific Ocean and under Beaverton just one day earlier. They were much deeper.
The shallower the earthquake, the more energy that reaches the surface of the earth. That explains why people in 92 different zip codes across Washington & Oregon felt the earthquake. And despite the fact we have hundreds of earthquakes in Washington and Oregon each year, only about a dozen or so (it varies a bit) are felt. That makes situations like this one pretty rare.
Electronic Seismographs Record The Earthquakes Across Vancouver, Gresham & Under Mt. Hood
And finally, because I’ve been asked about this already, here’s a very rough estimate of the Mount St. Helens Seismic Zone where quakes are very common.
Clearly, this earthquake was not in that zone. The last ‘felt’ earthquake with an epicenter right near Amboy–prior to this one–was on October 19, 2011. But it was just a 2.7 and was only felt in an area much closer to the epicenter.
Is this is sign of more quakes to come? Or the “Big One” about to happen? Uh, better go find a quarter and flip it in the air–let me know what it comes up with!