“If I were to hazard a guess, I’d say that this area is still rebounding somewhat from the retreat of the ice over 13,000 years ago.”
You may well be correct. That part of Lake PDO was under a LOT of ice pushing down on the crust. Or, it could be a strike-slip fault like the BIG one at Mt. Borah.
Some of the great Lake Missoula floods flowed through that area. I’m sure that there are a lot of “silent” faults around here.
I live on Missouri Mountain in Sagle which is the granitic northern extension of the Idaho Batholith called the Kaniksu lobe. It felt like a giant helicopter was hovering over the house. Granite transmits Earthquake waves quite efficiently. There were fast vibrations with one big jolt at the end. I used to live in Alaska and I never felt one like this up there.
How was that last one?