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630 quakes in one week on Sarigan
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Posted on Aug 15 2005
The seismic swarm recorded by Sarigan’s seismic station continues, with at least 630 earthquakes occurring beginning last Tuesday.
The Emergency Management Office and the U.S. Geological Survey noted that more than 40 earthquakes have occurred daily since Saturday.
The agencies reported this development as Anatahan’s volcano continues to be in a state of constant eruption. Long-period earthquakes have also been occurring on that island.
In a joint report yesterday, the agencies said tremor levels on Anatahan ranged between 30 and 70 percent of peak levels.
They said ash emissions from the volcano rose to an altitude of about 15,000 feet early yesterday morning and moved in an east-southeast direction.
The plume extended at least 83 nautical miles from Anatahan. The agencies reported no ash plume over Saipan, unlike the situation two weeks ago.
The agencies reported no other earthquakes in other islands in the Northern Islands. A 5.8-intensity temblor shook Maug Island late Saturday afternoon, while the EMO also disclosed of ongoing volcanic activity on Pagan.
Maug lies at the northern end of the Marianas chain, flanked to the north by Farallon de Pajaros and to the south by Asuncion Island. It used to be inhabited by a small population, but the CNMI Constitution declared the island uninhabited for purposes of wildlife conservation.
Maug comprises three steep-sided islets—North Island, East Island, and West Island—encircling a central lagoon. They represent the remains of a volcano that was believed to have collapsed following a massive and explosive eruption. The islets rise steeply from the sea, often as near vertical or undercut cliffs.
In 2003, federal and local scientists who were part of the National Oceanic and Atmospheric Administration’s Oscar Elton Sette mission reported the discovery of a submerged volcanic crater that was showing signs of activity. Marine monitoring conducted on the island at that time showed that volcanic vents were releasing warm water of over 100-degrees Fahrenheit. Gas emissions were also prevalent underwater through gas bubbles.
