The graphic above says it all. Today at 10am (PST) 1pm EST there will be a tweetchat on the Cascadia Earthquake threat, and how to prepare. Use hashtag #CascadiaEQ to follow along and participate.
Today is the 316th Anniversary of the Magnitude 9 mega thrust quake that struck the Pacific Northwest in 1700. A quake that was only the latest in a long line of seismic events that tend to occur in that region every few hundred years.
I've written a number of Cascadia quake related blogs over the years which you may wish to revisit.