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Yellowstone updates from the YVO 9 January 2009

Posted by admin in activity reports, calderas, United States, Yellowstone.
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The Yellowstone Volcano Observatory (YVO) has released two new statements on the earthquake swarm that rumbled its way through Yellowstone in late December and early January.

The 6 January 2009 YVO update reports:

About 500 earthquakes occurred between Dec. 26 through Jan. 1. Three hundred of the earthquakes (including all >M2.0) have been reviewed by seismologists. There have been 86 earthquakes with M > 2.0 and 16 earthquakes > M3.0. About 200 smaller earthquakes have yet to be reviewed. Depths are difficult to determine accurately. The best located earthquakes have depths on the order of 3 to 10 km (1.8 to 6.0 miles). From Dec. 26 through Jan 2, the earthquake hypocenters appear to have migrated northwards, starting southeast of near Stevenson Island, with many of the latest events occurring near Fishing Bridge.

The recent swarm is well above typical activity at Yellowstone. Nevertheless it is not unprecedented during the last 40 years of monitoring. Swarms are the typical mode of occurrence of earthquakes within the Yellowstone caldera, with magnitudes ranging to > 4.0. The 1985 swarm on the northwest rim of the caldera lasted for three months, with earthquakes up to M4.9 and over 3000 total events recorded.

Magnitudes of earthquakes in this swarm range from zero to 3.9.

A further summary statement on the swarm, with graphics, was released by the YVO on 8 January 2009:

About 900 earthquakes occurred between Dec. 26, 2008 and Jan. 8, 2009 in the Yellowstone Lake area. Five hundred of the earthquakes (including all greater than magnitude 2.0) have been reviewed by seismologists. There were 111 earthquakes with magnitudes greater than 2.0 (> M2.0)and 18 earthquakes > M3.0. About 400 smaller earthquakes have yet to be reviewed. The largest earthquake during the swarm was a magnitude 3.9 on Sunday, December 28, 2008. […]

The recent swarm is well above typical activity at Yellowstone. Nevertheless it is not unprecedented during the last 40 years of monitoring. Earthquake swarms within the Yellowstone caldera are typical, with magnitudes occasionally ranging above 4.0. The 1985 swarm on the northwest rim of the caldera lasted for three months, with earthquakes up to M4.9 and over 3000 total events recorded.

With analysis of earthquakes and of ground motions accompanying the swarm still in progress, this is very much a preliminary report. No conclusions as yet, then, about the cause of the swarm, only the important negative conclusion that ‘there is no reason to believe that magma has risen to a shallow level within the crust or that a volcanic eruption is likely’.

Full statement: Yellowstone Lake Earthquake Swarm Summary as of 8 January 2009.

There’s also a new USGS CoreCast featuring an interview with Dr Jake Lowenstern, Scientist-in-Charge at the YVO, who talks about what’s been happening at Yellowstone and the work of the YVO in monitoring activity and keeping people informed. Dr Lowenstern has this to say about the earthquake swarm:

This is a very energetic swarm, and probably the most energetic swarm since 1985. So, it’s not unprecedented, on the other hand, it’s an energetic swarm, people were feeling it, and it’s an area where there are thermal features, and anytime there’s earthquakes near thermal features we worry about explosions of the groundwater system.

Dr Lowenstern also has some interesting comments about the explosion of information and speculation about this kind of event made possible by the internet, and where this leaves professional scientists concerned that information is used in a responsible way:

One of the amazing things we see during these kinds of events is how many people are out there looking at the data and trying to interpret it on their own. Sometimes they do a great job of it, sometimes they confuse other kinds of signals like wind and snowmobiles and other features that might look like earthquakes but indeed might not be earthquakes. So it’s a challenge for us not only to keep up with the science, but to keep up with the sort of furore out there, of people who are trying to do their own interpretations on the side, and to keep everybody happy and everybody thinking about the real endgame, of making sure that people are safe.

The USGS CoreCast interview with Dr Lowenstern is  available through this page: Is Something Brewing in Yellowstone?

Information
Global Volcanism Program: Yellowstone – information about the Yellowstone Plateau volcanic field (1205-01-)
Yellowstone Volcano Observatory – monitors activity at Yellowstone
University of Utah Seismograph Stations – UUSS home page, including Yellowstone updates
Yellowstone Region seismogram displays – near real-time seismogram traces for Yellowstone
USGS earthquake list for Yellowstone – constantly updated earthquake data for Yellowstone

The Volcanism Blog

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Comments

1. Scott Horvath (USGS) - 9 January 2009

Thanks a lot for posting the information about the Yellowstone and for linking to the USGS CoreCast episode on this subject.


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