There was a good Kathryn Schulz piece at the New Yorker entitled: ‘The Really Big One,’published in July 2015, which Nick Zentner at Central Washington University uses as his jumping-off point for discussion.
The above hour-long talk is designed for lay-people and starts with the basics, catalogues the current evidence, and leads to current understanding:
On average, every 250-500 years or so, the Cascadia Subduction Zone can rip {partially or} at once, and can generate an earthquake (with tsunami) of potentially 9.0 or greater {if all at once}. The last big one is known to have occurred 316 years ago, on January 29th, 1700.
Oh boy…
-This timeline is not exactly reassuring…
-People are keeping track of these {local} things.
-Out on the coast, there are layers of rocks, sediment and mud indicating a momentous and terrible night.
-Monitor all current seismic activity here.
**Fun fact: There’s also a different fault right under Seattle (running roughly along I-90), that let loose around 900 A.D., and sunk a whole flank of Mercer Island, leaving a ghostly underwater forest.
Because Seattle was under a glacier not that long ago, it’s a long way down to bedrock, and this means bad news for transferring energy during earthquakes: A big bowl of mud and looser glacial deposits, drumlins and hills prone to landslide, ending abrubtly in water, does not a good recipe make.
Check it out: