The source of the seismicity isn't necessarily magmatic in origin -- not necessarily due to movement of magma. It may be due to plate movement. The seismologists' determination of the epicenter's depth will tell you -- the Nazca plate is present at depth, but the depth is very great in Wyoming, near the leading edge of the plunging overridden plate, much deeper than the Yellowstone magma chamber. (National Geographic had a good article on the Yellowstone hot spot recently.)
The hot spot, of course, is connected by a magma feeder to the magma chamber; this feeder penetrates both plates and has emplaced the magma body in the North American plate.
One temblor probably does not signal a problem. Swarming low-intensity quakes would be another matter.
Are you talking about Yellowstone or New Madrid?
I don't know that any of us thought that. What I found curious is the lack of mention of it virtually anywhere in the news.
My understanding is that in an area of known seismic activity, occasional events like this are a kind of safety value. The thing to worry about is NO activity, IOW, the pressure not being released.
But then again, geology is not my area of specialty. You want to talk tornadoes, I'm game but rocks? I'll leave that for the geologists.