Earthquakes have rattled California in recent days, causing fires and wrecking buildings and roads. And in late June, a series of quakes were recorded off the Oregon Coast.

But these seismic events aren’t related, said Don Blakeman, a geophysicist from the U.S. Geological Survey. And they aren’t precursors to the Big One, a nearly inevitable, massive Cascadia Subduction Zone earthquake expected to do enormous damage to Portland and the Pacific Northwest.

Thursday and Friday, magnitude 6.4 and 7.1 earthquakes struck in Southern California. According to The Associated Press, Friday’s quake was the strongest in the area in nearly 20 years.

Weeks earlier, a series of eight earthquakes were reported more than 200 miles off the coast of Oregon. The quakes were recorded at magnitudes between 3.2 and 5.4, according to data from the Geological Survey.

The earthquakes in Oregon and California are not directly connected, said Chris Goldfinger, an Oregon State University professor and earthquake geologist. In an email, he said the only connection is that the quakes are on the same Pacific North America plate boundary.

That entire plate moving around on the Earth’s surface with little sections of faults breaking is what causes these earthquakes, Blakeman said. He said the region is seeing a regular number of earthquakes.

Blakeman said a larger earthquake can trigger another quake, but they usually happen in a relatively close area.

"A magnitude 3.5 quake in Oregon is not going to trigger one of these 6.4, 7.1 earthquakes in California,” he said.

For people who live in fairly seismically-active areas, Blakeman said it’s a good idea to make your house safer in the event of an earthquake. He said it’s important to do basic things like screw in water heaters and tall bookshelves.

“Nothing is earthquake proof,” Blakeman said. “Just be prepared.”

-- Peter Talbot

ptalbot@oregonian.com

503-221-5772; @petejtalbot

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