You said — For all the trips I’ve taken to Yellowstone, I’ve never felt an earthquake while walking around in the park.
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I was just getting back in the car with my daughter (a youngster at the time) and she hopped in and I got in after her and then the car started rocking back and forth. I thought, at first, that she was jumping up and down in the back seat of the car (she did that sometimes... :-) ...). So, I turned around and was going to tell her to stop it, but she wasn’t doing it.
People who had been in their cars, at the time, jumped out of them and were looking around. My car was rocking back and forth, and I got out, too. When I had been in the car, just before getting out, I could hear the gas in the tank really sloshing around.
It wasn’t too long of one, but it was definitely one of the bigger ones. Most of them are very small (of those 1,000 or so a year that hit Yellowstone, normally). But, on the material that tourists get, I did notice a warning about being on the boardwalks when an earthquake hit. It was possible that someone could lose their balance and fall off the boardwalk, and into the surrounding area, which could be really hot water or mud or whatever (for whatever the boardwalk was going around in).
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You mentioned an earthquake in 1964, well there was one not too many years ago, that I remember quite well, the “effects” felt in the Portland area, in the year 2001.
A blurb from an earthquake website — “The earthquake most widely felt in Oregon was the February 28 Nisqually earthquake, centered near Olympia, Washington. The deep-seated, magnitude 6.8 event was felt throughout most of Oregon and as far away as Salt Lake City.”
Now that one rocked the building I was in, a Condo unit, third floor up, for a full minute. The building was really rocking on that one, and being up on the third floor, I was starting to think that this earthquake was going to go into a full-blown all-out one, since it had not quit for about a minute. I was thinking that, at any second, it could go “big”, because of how long it was going and going... LOL... I was just about ready to get out of the building, because I thought it was going to come down... :-)
Of course, at the time it happened, I didn’t know it was centered in Olympia, Washington.
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Then there was the “Spring Break Quake” in Portland, in 1993...
Quote from Wikipedia — The Scotts Mills earthquake (often referred to locally as the “Spring Break Quake”), which occurred in the U.S. state of Oregon on March 25, 1993 at 5:34 a.m. PST, with ML = 5.6, was the largest earthquake in the Pacific Northwest since the Elk Lake and Goat Rocks earthquakes of 1981.
I happened to have gone to work early and was in the office of a three-story building, on the bottom floor and it hit the building, two times, really hard, like some big semi-truck had smashed into the building and then things started rocking. Well, that was one time that I didn’t wait two seconds and I was out of the building as fast as I could go. I stood in the street looking around and there were a few other people around in the streets, too, even though it was early in the morning...
That’s not all the earthquakes that have been in the Portland area or felt there, so it gets a bit interesting at times.
They say that Portland could be in for the “big one” at some time in the future (within possibly 50 years), with up to a potential 10.0 magnitude quake..., since it’s in the Cascadia Subduction Zone. I’ve seen them say 9.0 and a few articles I’ve read have said 10.0. I guess they produce really big ones, and it could possibly go up that large. Also, it can possibly produce a tsunami, off the Oregon Coast of possibly 100 foot tall. I wouldn’t want to be on the Oregon Coast for that one... :-)
A couple years later I was working at the new data center. We had 6 ft racks with 4 Fujitsu Eagle drives (about 150 lbs each). The racks were lined up into multiple aisles about 30 ft long with a 2 ft aisle between the drive lineups. It was decided that a U shaped bar over the aisle would be advisable for earthquake bracing. The bars were installed and during the night there was a 5.8 earthquake in El Centro. The morning status message proclaimed the earthquake bracing was installed and successfully tested.
Another year later, I was working on some awful LU6.2 interface code between an HP-UX machine and an IBM mainframe. There was only one test machine in San Francisco, so I had to wait 3 weeks between my 1 hour test windows. My test window started at 5 PM. The IBM techs had a bunch of things to modify before we could start. Just as they were ready to start, the clock read 5:08 PM. The Loma Prieta earthquake was underway. My test window was lost for another 3 weeks. One of my co-workers was sitting in a dentist's chair on the 10th floor of a building in downtown San Francisco. The lights went out. He walked to street level in the fire escape stairs, then walked all the way back to his car...15 miles...because BART was out of service.
I had a college friend whose house was completely demolished by an earthquake in the Morgan Hill area.