The magnitude 4.6 earthquake in Snohomish County Friday is considered a small earthquake. It left some noticeable by slight damage in places but that was on a pretty low scale. 

If this quake was a knock at the door, the next one could break it down. 

Consider these projections. 

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Seismologists estimate a quake in the South Whidbey Island Fault Zone, near where this series of quake happened, is capable of a magnitude 7.5. 

That’s considered very large. 

The Seattle fault could producer a magnitude 7. 

RELATED: Prepare to be on your own in a major Pacific Northwest disaster

But the Cascadia Subduction zone, running not only along Washington’s coast, but past Oregon down into Northern California, and up into British Columbia, Canada north of Vancouver Island, could create a magnitude 9 plus.

While Friday's quake didn't produce much damage, it should have alerted you to start listening and get your preparations started. 

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