More on the Yellowstone earthquake swarm at the supervolcano caldera. First, this piece of database analysis from an IT guy at Splunk puts the swarm into scary perspective:
I'm sending you this email with some information I've gleaned from the USGS archives. I'm analyzing the ANSS data (http://www.ncedc.org/cnss/) in an install of Splunk, which is a timeline based search and reporting engine. I have 30 years of data in the system, with about 2M quakes total. It makes doing graphs and adhoc investigations faster than dealing with the USGS limited search forms. Disclaimer: I work for Splunk as their evangelist, and spend a lot of time studying various timeline based textual data and writing interesting apps for the software. I am not an earthquake expert by any means.
Using the ANSS data, I discovered the number of 2.5 or higher quakes in the *general* Yellowstone area for the decade of the 1980s was 128. The number of 2.5 or higher quakes for the region directly around the lake in the *last 4 days* was 30.
Again, for 2.5 mag or greater quakes:
Entire region of Yellowstone for 10 years = 128 quakes
Area just around Yellowstone Lake last 4 Days = 30 quakes
The entire 1980s of 2.5 or higher quakes in the vicinity of the lake was a paltry 4 quakes. Doing a quick back of the envelope calculation using the number of quakes and the intesities, the activity over the last 4 days has released roughly 100x the amount of energy released in the entire 1980s for the same general region. In the last week alone there have been 10 quakes of magnitude 3.0 or greater around the lake, with one as high as 3.8.
Also here is a pretty good summary of events from the Yellowstone Volcano Obervatory:
December 2008 Yellowstone Earthquake And Ground Deformation Summary
Yellowstone seismicity increased significantly in December 2008 due to an energetic earthquake swarm that commenced on December 26. This swarm, a sequence of earthquakes clustered in space and time, is occurring beneath the northern part of Yellowstone Lake in Yellowstone National Park. As of this writing, the largest of these earthquakes was a magnitude 3.9 at 10:15 pm MST on Dec. 27. Through 5:00 pm MST on Dec. 31, the sequence had included 12 events of magnitude 3.0 to 3.9 and approximately 20 of magnitude 2.5 to 2.9, with a total of at least 400 events large enough to be located (magnitude ~1 or larger). National Park Service (NPS) employees and visitors have reported feeling the largest of these earthquakes in the area around Yellowstone Lake and at Old Faithful and Grant Village.
The hypocenters of the swarm events cluster along a north-south-trending zone that is about 7 km long. The vast majority of the focal depths are shallower than 5 km. It is not possible to identify a causative fault of other feature without further analysis.
Analysts are currently processing the backlog of seismic data from these events. The current analyst-processed catalog is believed to include all events of magnitude 2.5 and greater through Dec 31 at 5 pm MST, but hundreds of earthquakes remain to be processed. The total of more than 400 locatable events is based on automatically-determined locations and magnitudes for the swarm events.
The December 2008 earthquake sequence is the most intense in this area for some years. No damage has been reported within Yellowstone National Park, nor would any be expected from earthquakes of this size. The swarm is in a region of historical earthquake activity and is close to areas of Yellowstone famous hydrothermal activity. Similar earthquake swarms have occurred in the past in Yellowstone without triggering steam explosions or volcanic activity. Nevertheless, there is some potential for hydrothermal explosions and earthquakes may continue or increase in magnitude. There is a much lower potential for related volcanic activity.
The National Park Service in Yellowstone has been kept fully informed of the ongoing seismic activity via electronic means and by phone contacts with the University of Utah and the U.S. Geological Survey USGS). The Wyoming Office of Homeland Security is reviewing Earthquake Response Plans and monitoring seismic activity.