WY is actually pretty active with low level geologic events like this.
While going to school out there in 1984, I experienced a 5.5. Was taking a test at the time and the table and chairs started to bounce around a bit. We were in the basement of the building and I was about 2 seconds from saying: "Time's up, pencils down" and heading for the door to get out of the building, but as fast as it started, it stopped.
UBEE and I went through a 7.9 in Alask a couple years ago. Unbelievable how the ground moves! We had hundreds of "small" 4.5 aftershocks for a couple days after it.
The hills are a shaken cause they know we'll be there! Yeah, right! LOL! Either they are scared, or telling us to be! What do you think? My feeling is the later of the two is likely the right answer. I have wanted & waited for over 20 yrs for the mountain riding experience, my first opportunity to go & this happens! Makes you wonder, is this one of those Here's your sign moments? Tough crap, reservations are made.-Mezz