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Seismic ‘slow-slip’ event happening now, but will it increase the chance of an earthquake?

SEATTLE - Seismologists are monitoring a seismic event that they say is happening right now. It’s called a “slow-slip” event. According to the Pacific Northwest Seismic Network at the University of Washington, this event happens about every 14 months.

PNSN has been tracking it for about two decades, ever since the Nisqually earthquake.

Think of Earth as large puzzle pieces. The land that we’re on right now is called the North American Plate. There is another tectonic plate called the Juan de Fuca plate that is just off our coast. According to seismologists, the offshore plate (Juan de Fuca Plate) is moving underneath the North American plate -- or slipping, slowly.

“Once in a while, the North American plate slides just a little bit, a few inches toward the west. So, the region that’s just under the Olympic Peninsula or on Vancouver Island is moving just a few inches to the west during these slow slip events,” said Harold Tobin, director of the Pacific Northwest Seismic Network.

But what’s concerning for some seismologists, and there is a difference in opinion about this, is that the slow-slip event will slightly increase the chances of earthquakes, or even the “big one.” Typically the plates are locked, according to Tobin. But because the plates are moving, there is concern that the “slip” will cause an earthquake.

“There is some science in the possibility that maybe it slightly increases the probability of an earthquake happening. The jury is still very much out on that. I would say nobody should worry that that means an earthquake is imminent. There's probably a small change in the likelihood of a subduction earthquake during a time like this,” said Tobin.

Tobin says the movement between the plates is very deep underneath us, so it's unlikely that we will feel anything.

That being said, there is a difference in opinion when it comes to this event.

“We have an increased chance of a big earthquake initiation because the slip is adding load to the bottom edge of the fully locked zone of the Cascadia Fault,” said PNSN seismologist Bill Steele.

The Cascadia Fault is the one that scientists all agree could cause the "big quake."

But Steele also points out that there have been several of these slow-slip events that didn’t cause a big earthquake over the past 300 years.

Nonetheless, what scientists can agree on is people should always be prepared, and that includes putting together emergency kits, just in case.

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