The Great Ones-Some Links To Earthquakes On the Cascadia Subduction Zone

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.

Below the surface

**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:

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