Yellowstone Earthquake Swarm Puzzles Scientists
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The earthquake activity in Yellowstone that the article below reports on has
continued since it was written. Yesterday, January 2nd, was an especially
active day with six 3.0 to 3.5 tremors. You can find a list of current
quakes at this location:
--- David Sunfellow
YELLOWSTONE EARTHQUAKE SWARM PUZZLES SCIENTISTS
December 30, 2008
A swarm of small earthquakes in Yellowstone National Park is the most
intense measured there in years, leaving scientists puzzled.
The region is known for such swarms -- 1,000 to 2,000 quakes occur annually
in the park. Yellowstone's 10,000 geysers and hot springs, including the Old
Faithful Geyser, may be the result of this geologic activity.
But the latest shaking is notable for the number of tiny temblors and their
intensity, according to a statement yesterday from the University of Utah,
where scientists monitor seismic activity in Yellowstone. (Yellowstone is
located mostly in the northwest corner of Wyoming.)
The largest of the earthquakes was a magnitude 3.9 at 10:15 pm MST on Dec.
27, a day after the swarm began. The sequence has included nine events of
magnitude 3 to 3.9 and approximately 24 of magnitude 2 to 3 at the time of
this release. A total of more than 250 events large enough to be located
have occurred in this swarm.
"Scientists cannot identify any causative fault or other feature without
further analysis," according to the statement.
Most of these temblors would not be felt by humans. Earthquakes generally
have to exceed magnitude 4.0 to cause light damage.
Scientists wonder if the shaking might presage a larger event. This month's
swarm is the most intense in this area for some years, scientists said. It
is centered on the east side of the Yellowstone caldera, a giant basin
created in a colossal eruption some 620,000 years ago.
Researchers have long predicted that the Yellowstone supervolcano will
eventually erupt again, with devastating consequences for much of the United
States. Half the country could be covered in ash up to 3 feet (1 meter)
deep, one study predicts. But those same researchers say nothing suggests
such an eruption is imminent. They point out, however, that Yellowstone
seems to blow its top about every 600,000 years.
Meanwhile, the region's deep secrets are still being revealed.
Last year researchers reported on unusual slow movement below the surface
that's tied to a newfound gradual sinking of the nearby Teton Range. And in
2006, scientists discovered that in the previous decade, the volcano had
risen nearly 5 inches.
"Could it develop into a bigger fault or something related to hydrothermal
activity?" wonders Robert Smith, a professor of geophysics at the University
of Utah. "We don't know," he said this week.
Smith and his colleagues said they'll continue to monitor the activity.
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Published by David Sunfellow
Phone: (928) 257-3200
Fax: (815) 642-0117
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Sedona, AZ 86339