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Sarigan seismic swarm calms down
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Posted on Aug 19 2005
The seismic swarm on Sarigan Island has been tapering off since Wednesday, the Emergency Management Office and the U.S. Geological Survey said.
Since Tuesday last week, though, Sarigan’s seismic station recorded more than 705 earthquakes.
The agencies also reported that tremor levels on Anatahan ranged from 25 to 50 percent of peak levels, but added that an earthquake triggered an equipment alarm, possibly indicating a strong volcanic eruption.
They said the alarm occurred at about 3:21pm Thursday and lasted one minute. The agencies also said that long-period earthquakes have been sporadic. Yesterday morning, the agencies said an ash plume from Anatahan’s volcano rose to 15,000 feet and moved northeasterly.
On late Monday to early Tuesday this week, seismicity on Anatahan triggered at least 10 alarms that indicated high eruptive activity. They said a similar scenario occurred on April 6, when the volcano spewed ash to 50,000 feet and emitted an estimated 50 million cubic meters of ash. Ash plume, though, could not be detected by satellite imagery. (John Ravelo)
