Faults under Oregon can trigger anytime, advanced warning system in the works

PORTLAND, Ore. — Wednesday's 4.0 magnitude earthquake rattled parts of Oregon and Washington. Windows rattled, items shook off shelving and people recorded feeling tremors as far away as southwestern Washington.

There was no major damage, although a small crack formed in the wall of a building in Scotts Mills, near the epicenter of the quake.

No one was hurt.

But geologists warn more quakes are possible.

Portland State University geology professor Scott Burns says there are dozens of faults in Oregon, some of them are more active than others.

The most potent is the Cascadia Fault, a seismic zone that stretches for almost 700 miles just off the Pacific Northwest coast. Based on current understanding of the fault's seismic history, scientists estimate quakes occur along the line roughly every 240 years. The last major earthquake occurred Jan. 9, 1700.

So, is Wednesday's quake in Scotts Mills a precursor?

Burns says it's unlikely. The Cascadia and Mount Angel Faults are two different types of faults.

Crustal faults quakes are caused by moving rocks in the shallow part of the earth's crust. Subduction is caused when two plates collide.

"You can have a precursor, but those are generally crustal quakes affecting the crustal quake, not a crustal quake affecting a subduction zone," Burns said.

Wednesday's earthquake originated from the Mount Angel Fault, which runs from about Scotts Mills under Newberg and up to Forest Grove, where it's locally known as the Gales Creek Fault.

In 1993, a shift in the Mount Angle Fault caused a 5.6 magnitude quake. It caused more than $25 million worth of damage.

The quake shook lawmakers, who realized they were in earthquake country.

Until the 90s, Oregon lacked building codes for earthquakes. The 1993 quake changed that.

Burns says an estimated 75 percent of the state's infrastructure -- buildings, housing, bridges, dams -- is not built to withstand a significant earthquake.

Work is underway on an early warning system that could save lives in the event of a major earthquake.

It's called ShakeAlert. It's currently in the beta-testing stages.

Using strategically placed monitoring stations, ShakeAlert would send warning messages within a few seconds of an earthquake to mobile devices and computers. The alerts could give enough time for a person to seek shelter or get to safety and alert emergency crews to get in place and ready to respond.

Oregon Seismic Network Manager and ShakeAlert Technician Leland O'Driscroll says the system performed well Wednesday.

"It took eight seconds first for the warning to be produced," O'Driscoll said. "Once that warning was produced that meant Salem had three seconds of advanced notice and Portland had eight seconds of advance notice."

Notice to prepare, O'Driscoll clarified.

It doesn't seem like much, but every second counts during a disaster.

For really large events, like a subduction zone quake, alerts would be triggered within seconds, notifying Portlanders they would have a few minutes to get to safety before tremors hit.

A limited public rollout will occur late next year. Schools, utility companies, transportation agencies, first responders and medical staff would receive the application first. O'Driscoll says he expects ShakeAlert to be more widely available the following year.

President Donald Trump zeroed out ShakeAlert's budget following his election, but Congress restored that funding and ShakeAlert has already secured funding for the upcoming fiscal year.

ShakeAlert staff and stakeholders are working to install more monitoring stations across Oregon and Washington.