I am a geologist and a native Montanan, I've followed the activity in the park most of my life. Here is the YVO interpretation of the swarm's significance (from Jan 28)
Yellowstone Volcano Observatory scientists still consider that the swarm events are likely the result of slip on pre-existing faults and are not thought to be caused by underground movement of magma. Currently there is no indication of premonitory volcanic or hydrothermal activity, but ongoing observations and analyses will continue to evaluate these different sources.
Earthquake swarms are common for the park. This one is unusual for the number - but also because of the enhanced intrumenation in the park to monitor them. Interesting, but I wouldn't cancel my trip to the park this summer over it.
So this is just a “Rumbling” as in my Intestines? ;)