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4.9-intensity quake rocks Marianas
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Posted on Nov 11 2005
Anatahan’s volcano has not emitted significant amounts of ash since early September, but local and federal monitoring agencies disclosed that a regional earthquake with a magnitude of 4.9 occurred recently.
In a joint report, the CNMI Emergency Management Office and the U.S. Geological Survey said that the quake occurred around 11:57am Sunday and was located about 100 miles southwest of Guam.
In the past weeks, earthquakes with magnitude of 4.6 and 4.7 were also located near Maug and between Anatahan and Pagan.
However, the agencies said that seismicity on Anatahan has remained low, amounting only to a few percent of peak levels recorded last June. They said small long-period earthquakes occur very infrequently.
Volcanic earthquakes indicate magmatic movement that may lead to an eruption. Rare long-period quakes indicate low magmatic activities, and an immediate volcanic eruption is not likely.
The Anatahan volcano’s strongest eruption occurred on April 6, with the volcano spewing ash to 50,000 feet. The USGS and the EMO estimated the volume of ash emissions in that eruption at about 50 million cubic meters.
The volcano first erupted on May 10, 2003 after centuries of dormancy, with ash plume rising to an altitude of over 30,000 feet and covering over 1 million square kilometers of airspace above the Pacific Ocean. That eruption, which ceased by mid-June that year, deposited about 10 million cubic meters of material over Anatahan island and the sea. (John Ravelo)
