Archived Update

June 7, 2003
12:00 P.M. Pacific/Saipan (GMT+10 hours)

The eruption of Anatahan Volcano continues today. An eruption column is rising to about 2,500 m (8,000 feet) above sea level, and ash is falling on the western part of the volcanic island. During a trip to Anatahan late yesterday afternoon, a team of observers from the Emergency Management Office (EMO) and scientists from the U.S. Geological Survey identified what may be a fresh mound-shaped feature called a lava dome in the volcano's east crater, the source of the eruption since it began on May 10. The team also repaired the EMO's only seismic-monitoring station on the volcano. EMO is now receiving seismic data from the station, located about 1 km (0.6 miles) from the site of eruption.

Analysis of the earlier earthquake records shows that the explosive activity was preceded by many earthquakes starting 12 hours before the eruption began. During the first two days of the eruption, on May 10 and 11, the seismic records were dominated by as many as 100 earthquakes per hour. The largest earthquake had a magnitude of about 3. Since then, very few earthquakes have occurred, but nearly constant ground shaking, known as volcanic tremor, has dominated the seismic activity. The tremor is likely caused by the constant emission of ash and gases. Within the past 36 hours, the earthquake records show a constant level of tremor.

Contact persons:

Juan Takai Camacho, Geophysical Seismic Technician, EMO Saipan; tel: (670) 322-9528, fax: (670) 322-7743, email: juantcamacho@hotmail.com

Frank Trusdell, Geologist, USGS; tel: (808) 967-8812, fax: (808) 967-8890, email: trusdell@usgs.gov