The quake is actually frighteningly close (about 200mi from the epicenter) to the Yellowstone Super Caldera in northwest Wyoming.
The 6.5 Earthquake Was About 78 Miles from Boise. According to USGS.gov, this earthquake was reported at 44.448°N 115.136°W about 72 km west of Challis, Idaho.
So what would happen if the Super Caldera would erupt?
If the super volcano underneath Yellowstone National Park ever had another massive eruption, it could spew ash for thousands of miles across the United States.