There are dozens of earthquake faults across Oregon, including one through Portland

The Cascadia Subduction Zone earthquake gets headlines around the Pacific Northwest, but geologists say the next big earthquake you feel will likely come from a fault somewhere else.

Scientists say there are dozens of other faults running through Oregon and Washington. These crustal faults are similar to the fault that caused two large earthquakes in southern California and can produce large earthquakes too.

One such fault, the Portland Hills Fault, runs through the city of Portland.

Ian Madin, a senior scientist and earthquake hazard geologist at the Department of Geology and Mineral Industries (DOGAMI), says the Portland Hills Fault runs along the West Hills, through Portland, and toward Milwaukie.

“It’s a very difficult one to study because someone built a city on top of it,” Madin said.

Madin says this fault can unleash a 6.8-magnitude earthquake every 5,000 to 10,000 years. He isn’t sure when the last earthquake happened, possibly about 12,000 years ago. He said they don’t have enough information to say if it’s likely another large quake could happen soon.

“It's a much rare event, but we're sitting right on top of it,” Madin said. “That makes the shaking and damage from that earthquake much, much worse.”

Madin says a big quake along this fault would cause more damage to the city of Portland than a Cascadia quake. While there could be damage across the Pacific Northwest from a Cascadia earthquake, Madin says a quake on the Portland Hills Fault would only cause local damage.

“It's likely the next big earthquake we have in Oregon or Washington will be on one of these crustal faults because there are just so much of them,” said Madin.

Research suggests a large earthquake in the Cascadia Subduction Zone happens about every 500 years. The last known earthquake there was in 1700.

What’s more, geologists are regularly finding new fault lines across Oregon.

“Many of these are in areas where we might not expect,” said Madin.

Geologists recently found a new fault running through Mount Hood. Madin said it can cause a 7.2 magnitude earthquake. They also found new faults near Hagg Lake.

Madin says if you prepare yourself for the Cascadia quake, then you will be prepared for any other earthquakes in the region.

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