I did my due diligence researching earthquakes and tsunamis for Tahoma’s Hammer. We had a few “felt ‘ems” in the 90’s, a real eye-opener for this native Texan. The one that worried me, though, came in February of 2001—and it was a 30-mile-deep M6.8! I think what scares most people about earthquakes is that you can’t see them coming. I grew up near tornado alley, and survived Hurricane Alicia in Houston in 1981. But…
You can see hurricanes coming for days and while tornados can sneak up on you, you can still usually see the predictable storm-cells developing thanks to modern technology. But earthquakes… well, they just show up without an invite and ruin your party.
FEMA says that Washington State is the 2nd-most susceptible, after California, to earthquake loss. We have more than 1000 earthquakes every year, the vast majority of which are near Puget Sound and never felt.
As these photos show, there are a huge number of faults that run under Puget Sound. One thing people don’t realize is that shallow earthquakes have a much more devastating effect. A M6.8 six miles deep is much more devastating than one at 52-miles deep. An earthquake’s depth is the hardest factor to pinpoint accurately. There are so many variables to earthquake intensity that it isn’t accurate to draw a simple mathematical comparison.
Deep earthquakes are more widely felt, but they lose a lot of energy traveling through crust. One of the scariest aspects about the Seattle fault-lines is their depth. Many of them are just barely in the crust. But none of those will compare to Cascadia.
Cascadia is a shallow and massive subduction zone formed by a dense ocean-plate pushing itself under a less-dense continental plate. When it releases—Not IF, But WHEN—life in this country will be unalterably changed. This is why the book’s various narrative sections go so deeply into the trickle-down effects to the rest of the country. In many ways, I probably under-guessed how bad things will be. And THAT scares me…
What scares you the most about “the big one?” Leave it in the comments!
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