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Последните се случија на Хаити, Кина
и ова е за јелоустоун
By KIRK JOHNSON
Published: January 31, 2010
DENVER — In the last two weeks, more than 100 mostly tiny 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 plans were in place to intensify observations 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 area.
Researchers at the University of Utah’s Seismograph Stations who have tracked Yellowstone swarms said they thought it was coincidental that another big swarm of more 1,000 quakes had struck the park just over a year ago. At the time, it was the second-biggest cluster recorded there. The largest swarm was in 1985, when 3,000 earthquakes struck over three months.
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 researchers use the park’s geologic wonders, like Old Faithful — which spews steam and water on schedule, plus or minus 10 minutes — as indicators of the effects of quake activity. He and his team look for changes in water temperature, or mud plumes in hot pools that otherwise run clear. This swarm, he said, seems not to have affected any of those natural monitors, though he emphasized that analysis was continuing.
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 park visitors had been encouraged to help with the research by telling park officials if they felt the ground shake.