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Yellowstone earthquakes continue
Alert to be issued?
2 Feb 10 - Since January 17, 2010 Yellowstone has had 1,620
earthquakes, the second largest swarm ever recorded. The swarms have
been steady at about 10 miles in depth and they have subsided a few days
ago.
"The vast majority of the quakes have been too small to be felt," says
this article in the Powell Tribune. "The highest quake has been a
magnitude 3.8, and no injuries or damage have been reported. It
typically takes above a magnitude 5 to cause damage."
A reader tells me that Yellowstone might go on first stage alert soon
because the depth of the quakes has risen and the number has vastly
increased, but I have not yet been able to confirm that.
Yellowstone sits atop a gigantic volcanic caldera, which formed about
640,000 years ago. Since then, approximately 80 relatively nonexplosive
eruptions have occurred. Of these eruptions, at least 27 were rhyolite
lava flows in the caldera, 13 were rhyolite lava flows outside the
caldera and 40 were basalt vents outside the caldera. Some of the
eruptions were approximately the size of the devastating 1991 Pinatubo
eruption in the Philippines, and several were much larger. The most
recent volcanic eruption at Yellowstone, a lava flow on the Pitchstone
Plateau, occurred 70,000 years ago.
The Yellowstone Volcano Observatory, which monitors the caldera, has
said it is “confident” that the recent quakes are the result of shifting
and changing pressures in the earth’s crust — not due to an increase in
volcanic activity.
“We’re not worried about Yellowstone blowing up. Not even a little bit,”
said Glenn Koelling, a winter keeper at Canyon Village.
See entire article by CJ Baker:
http://powelltribune.com/index.php/content/view/3018/2/
Thanks to Kenneth Lund for this link
See also:
http://www.quake.utah.edu/helicorder/ymr_webi.htm
http://www.seis.utah.edu/req2webdir/recenteqs/Maps/111-44.html
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