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Originally posted by Shirakawa
reply to post by PuterMan
I'm also trying to download another version with smaller earthquakes (with magnitude lower than 1.0), but they take forever to process from the ANSS website.
More than 800 earthquakes occurred between Dec. 26 and Jan. 8. Many of those quakes were too small to be felt. Even so, University of Utah geophysicist Robert Smith says it was the most intense swarm recorded in Yellowstone since a swarm that rattled the West Yellowstone area in 1985. Smith theorizes the quakes were caused by hydrothermal fluids expanding along a fault zone. A similar event is thought to have caused the 1985 swarm.
Smith said the recent swarm is helping scientists understand how tectonic and volcanic forces can work together during an earthquake, and how earthquakes can interact with one another over long distances.
Scientists wonder, however, how the swarm might affect the park's thermal features.
The earthquakes could even change the routine rise and fall of the Yellowstone Caldera. The caldera, a 37- by 25-mile volcanic feature at the center of the park, rests upon a magma plume that extends roughly 400 miles beneath the Earth's surface.
The 1985 swarm coincided with the start of several years of caldera subsidence. The caldera had been gradually rising for decades before 1985.
Here's what they concluded: This recent swarm of quakes amounted to the second biggest swarm in about a half-century of Yellowstone observations. There have been 69 swarms since 1989 alone. And the total amount of energy released in this swarm, says Smith, was the equivalent of just one magnitude 4.5 earthquake.
Dr. Lowenstern did grant that having the swarm take place under Yellowstone’s largest lake — more than 300 feet deep — added to the sense of mystery. “If there was a swarm under land, you could easily look for changes in hydrothermal activity — if magma was coming out, you would see it,” he said. “We don’t know if there are changes beneath the lake.” “If we had another swarm in six months, it certainly wouldn’t surprise me,” Dr. Lowenstern said.