Today there has been a series of earthquakes in Southern Colorado, near the town of Trinidad. One of them is a shallow 5.3 magnitude earthquake. There are several other smaller earthquakes, most of them aftershocks around it. After looking at the terrain, I see nothing unusual about the area other than signs of possible scarping, but that I can't really determine without actually being there. I have looked at the area via Google Earth images. The USGS has not released to the public any waveforms, so at this point, until I look deeper, I cannot say whether this is volcanic harmonics or just a normal tectonic earthquake series. I'm looking further into it over the next few days. Earthquakes of this magnitude are not common in Colorado, and it was very widely felt as far as Fort Collins and Denver!
The quakes struck in an area that is known for occasional earthquake swarms, but there is no known faults in the area. This is the largest earthquake to hit the state of Colorado since 1967.
Here is the USGS link to the main earthquake:
Here is an article in the news about it: