Quakes at Yellowstone 3 January 2009Posted by admin in activity reports, calderas, United States, Yellowstone.
Tags: calderas, volcanic activity reports, Yellowstone
The calderas of the Yellowstone Plateau volcanic field provide a favourite agent of doom for those who like to brood on the destruction of civilization through a catastrophic ‘supervolcano’ eruption. Even leaving aside the supervolcano angle, or at least putting it into perspective (‘The probability of a large caldera-forming eruption within the next few thousand years is exceedingly low’, says the USGS), this is a very active volcanic zone that has seen large-scale eruptive activity over the last two million years. Yellowstone has seen three huge caldera-forming eruptions 2.1 million years ago, 1.3 million years ago and 640,000 years ago, the eruption of extensive rhyolitic lava flows between 150,000 and 70,000 years ago, and several major hydrothermal eruptive episodes during the past 10,000 years. The news of ongoing earthquake swarms at Yellowstone over the past week is thus of great interest.
There is nothing unusual about earthquakes at Yellowstone: the Yellowstone Volcano Observatory (YVO) says that 1-20 earthquakes are normally recorded every day. At times, however, earthquake activity increases significantly, with a rise in the number of earthquakes, all of about the same magnitude (i.e. no distinguishable mainshock or aftershock) occurring over a short period – an earthquake swarm. The YVO relates that recent notable swarms occurred in 1977, 1985, 1995, 1999, and 2004. The latest significant swarm is under way now, and it is the largest since 1985, says the YVO’s top scientist, Dr Jacob Lowenstern.
The current earthquake swarm began on 26 December 2008 with the University of Utah Seismograph Stations recording quakes of magnitudes under 3.5 located beneath Yellowstone Lake. The swarm continued and intensified on 27 December with magnitudes of 2.5 to 3.2, the larger of which were felt by people in the Yellowstone Lake area. On 29 December the YVO reported that more than 250 events had taken place since the swarm began, with the largest quakes up to then registering magnitudes between 3 and 3.9. (Source: YVO updates archive for December 2008.)
On 1 January 2009 the YVO reported that the swarm was continuing:
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.
By 2 January more than 500 earthquakes had been recorded with depths ranging ‘from ~ 1km to around 10 km’ and the activity showing a northwards migration. The YVO sees no cause for concern in this earthquake swarm, but warns that ‘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’. (Source: YVO updates archive for January 2009.)
Overall, the message from the Yellowstone Volcano Observatory and the USGS is that this earthquake swarm is within the parameters of normal behaviour for Yellowstone (and indeed the alert level remains at ‘normal‘) and is a product of hydrothermal activity rather than magma movement. To quote Dr Lowenstern of the YVO:
At this point, any kind of volcanic eruption is a long shot … the most likely thing is that the swarm will continue, perhaps for weeks, and then will end without any other related activity … before any kind of an eruption we’d expect a whole lot of change in the ground deformation as measured by GPS. Nothing has changed over the past week.
The latest: Seismic data from the Yellowstone stations for today, 3 January 2009, shows a falling off in intensity since around 21:45 UTC yesterday.
There’s further coverage of Yellowstone developments at Greg Laden’s blog (also here – don’t miss the comments – and an earlier article here), and Dr Erik Klemetti’s Eruptions. For another angle, see Alan Sullivan’s Fresh Bilge. US News & World Report is also paying attention to Yellowstone: see James Pethokoukis’s latest, ‘Earthquakes at Yellowstone Supervolcano: Update’. That’s in the Capital Commerce blog, in the financial section. US News‘s so-called ‘Science’ section doesn’t bother itself about this kind of thing.
Scientists watch unusual Yellowstone quake swarm – Associated Press, 29 December 2008
Yellowstone earthquake swarm puzzles scientists – LiveScience, 30 December 2008
Multiple tiny earthquakes rattle Yellowstone – Scientific American, 30 December 2008
A spurt of quake activity raises fears in Yellowstone – Time, 1 January 2009
Earthquake swarm at Yellowstone supervolcano: update – US News & World Report, 1 January 2009
More small quakes rattle Yellowstone National Park – Associated Press, 2 January 2009
Earthquakes at Yellowstone supervolcano: update – US News & World Report, 3 January 2009
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