At least that many. Does anyone remember the big 7.5 magnitude 1959 Yellowstone quake that killed at least 28 people in a landslide that dammed a river and created a new lake? The whole region's a seismic crapshoot, the continuation of a geologic process that began millions of years ago with creation of what's called the Yellowstone Hot Spot.
Yes, I remember that one, to this day. It was really big news when it happened.