Steaming, gurgling mudpots in the active hydrothermal system of Yellowstone.
For those of you following Yellowstone (I think there might be a few of you), I've plotted up the earthquakes since 1/27 (see below) - and sure enough, although there is a lot of scatter, they are getting shallower - however what this exactly means is unclear. You can see my plots from 1/22-28 here. As many of you have mentioned, a caldera like Yellowstone is a big interconnected system, so a solely tectonic source of this is still possible as the displacement migrates through the fractured caldera rocks.
This all being said, YVO's current status statement still reads:
" At this time, YVO scientists and their collaborators have detected no anomalous ground deformation, strain, or increased thermal activity that could indicate precursory activity to phenomena such as steam explosions or volcanic eruptions. As such, the Volcanic Alert Level remains at Normal (Aviation Color Code of Green)."
So, again, without abundant evidence to suggest otherwise, the swarm has shown no indications that this is magma related. The earthquakes are shallower right now, but again, we need to look at this information with an abundance of caution. YVO posted yesterday a summary of the current earthquake swarm and an brief history of swarms to put this one in context along with a description of all the monitoring that occurs at Yellowstone - so if you are concerned about the swarm, be sure to check it out. This caldera is not solely a magmatic feature - the process of caldera-forming itself involves breaking the crust along a ring fracture. This means that the area is littered with thousands (millions?) of fault systems related to the caldera. Trust me, I'd be fascinated by the idea that a new dome might be erupting at Yellowstone (i.e., NOT A SUPERVOLCANIC ERUPTION), which is the mostly likely scenario, but until the evidence tells me otherwise, this doesn't look like it.