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EMO restores seismic monitoring on Anatahan
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Posted on Apr 24 2005
Seismic monitoring of Anatahan has been partially restored after Emergency Management Office staff flew to the island Friday to repair its only functional seismic station there.
But the EMO and the U.S. Geological Survey said yesterday that seismicity on Anatahan remained constant despite Friday’s repair.
“Nevertheless, we infer that the current seismicity continues at the low, near-background levels seen since the explosive eruption of Anatahan on April 6,” the agencies said.
A plume of steam and ash continued rising from the volcano to about 10,000 feet, they said. The plume reportedly extended about 100 nautical miles west-southwest of Anatahan.
Last April 6, the volcano spewed out about 50 million cubic meters of ash. The eruption sent clouds of ash to an altitude of 50,000 feet, resulting in the cancellation of international and domestic flights. Saipan also experienced ashfall.
The EMO team that flew to Anatahan last Friday included geophysical seismic technician Juan Takai Camacho. Before the repair, Camacho said last week that all seismic stations that were installed on Anatahan to monitor the volcanic activity on the island have been malfunctioning, hampering the EMO’s monitoring capability.
The only functional seismic station on that island got seriously degraded, with seismic signals becoming unreliable beginning last Monday afternoon. Two other seismic stations have malfunctioned earlier.
The EMO continued to warn aircraft to avoid passing near Anatahan. Although the EMO said that the volcano is not currently dangerous to most aircraft within the CNMI airspace, it added that conditions might change rapidly. It advised aircraft to pass upwind of Anatahan or beyond 10 nautical miles downwind from the island and exercise due caution within 10 nautical miles.
The first historical eruption of Anatahan began on May 10, 2003, after hundreds of years of dormancy. A phreatomagmatic eruption characterized by steamy strombolian explosions sent ash to over 30,000 feet and deposited about 10 million cubic meters of material over the island and sea, according to the USGS and the EMO. (John Ravelo)
