*Great Earthquakes In Diverse Places

Hundreds of Earthquakes Are Rattling Yellowstone*

By KIRK JOHNSON
Published: January 31, 2010
The New York Times

DENVER --- In the last two weeks, more than 100  earthquakes a day, on
average, have rattled a remote area of Yellowstone National Park in
Wyoming, putting scientists who monitor the park's strange and volatile
geology on alert.

Researchers say that for now, the earthquake cluster, or swarm --- the
second-largest ever recorded in the park --- is more a cause for
curiosity than alarm. The quake zone, about 10 miles northwest of the
Old Faithful geyser, has shown little indication, they said, of building
toward a larger event, like a volcanic eruption of the type that last
ravaged the Yellowstone region tens of thousands of years ago.

The area is far from any road or community, and the park is relatively
empty in winter. Swarms of small quakes, including a significant swarm
last year, are relatively common.

But at a time when the disastrous earthquake in Haiti on Jan. 12 has
refocused global attention on the earth's immense store of tectonic
energy, scientists say that the Yellowstone swarm, if only because of
its volume, bears close observation: as of Sunday, there had been 1,608
quakes since Jan. 17.

"We're not seeing a pattern that is really discernible yet," said Henry
Heasler, a coordinating scientist for the Yellowstone Volcano
Observatory, a joint venture of Yellowstone, the United States
Geological Survey and the University of Utah.

Dr. Heasler said that plans were in place to intensify the level of
observation in case the swarm continued for a long time or got larger.
"We're ready to ramp up," he said, including using flights to monitor
the quake area.

Researchers at the University of Utah's Seismograph Stations who have
tracked Yellowstone swarms said they thought it was coincidental that
the park was struck just over a year ago by another big swarm of more
1,000 quakes. At the time, it was the second-biggest cluster ever
recorded at Yellowstone. The largest swarm occurred in 1985, when 3,000
earthquakes struck over a three-month period.

Last year's swarm, beneath northern Yellowstone Lake, had a specific
track of alignment, with the earthquakes moving north and growing
shallower from the initial quake area, said Robert B. Smith, a professor
of geophysics at the University of Utah and a science coordinator at the
Yellowstone Volcano Observatory.

The mostly smaller quakes in the current swarm, he said, are more like a
cloud, with no directional pattern, similar to what scientists saw in a
big swarm at the park in 1999. "We think the crust beneath Yellowstone
is highly fractured already, so we're getting stress release in these
earthquakes --- a displacement of millimeters," Dr. Smith said.

Dr. Heasler said that researchers use the park's geologic wonders, like
Old Faithful --- which spews steam and water on a predictable schedule,
plus or minus 10 minutes --- as indicators of the effects of quake
activity. He and his team look for changes in geyser water temperature,
for example, or mud plumes in hot pools that otherwise run clear. The
current earthquake swarm, he said, seems not to have affected any of
those natural monitors, though he emphasized that analysis was continuing.

Public attention to earthquakes in general has soared since the quake in
Haiti. For instance, visits to the United States Geological Survey's
Earthquake Hazards Program Web site increased fivefold after the quake,
to more than a million a day, compared with the numbers a month earlier,
an agency spokeswoman said.

Dr. Heasler said that visitors to Yellowstone had also been encouraged
to get involved and help with the research by telling park officials if
they felt the ground shake.