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U.S. Geological Survey, Vancouver, Washington
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington
Mount St. Helens Update
September 30, 2004 7:30 A.M., PDT
The alert remains at a Volcano Advisory. Overnight the seismic energy level increased slightly and remains elevated with a rate of 3-4 events per minute and now include events as large as magnitude 3.3. All earthquake locations are still shallow and in or below the lava dome. In addition, initial data from the GPS instrument on the lava dome that was repaired Monday morning suggest that the site moved a few inches northward Monday and Tuesday, but has since been stable. Such movement is not surprising in light of the high seismicity levels. A USGS field crew continued their deployment of GPS equipment yesterday in order to monitor any ground movement on the lava dome, crater floor, or lower slopes of the volcano. A gas flight yesterday morning measured no significant volcanic gas, as was the case on Monday. Another gas flight will occur this afternoon. Press conferences will be held today at CVO at 9:30 am and 2:30 pm to update the media. Today's field work includes further GPS data collection and a gas flight.
The current hazard outlook is unchanged from that outlined in yesterday's Volcano Advisory. Updated wind forecasts from the National Oceanic and Atmospheric Administration coupled with an eruption model indicate that the wind direction are out of the northeast. Therefore any ash clouds produced today will drift southwestward.
Confusion at yesterday’s press briefing at CVO regarding Alert Levels resulted in numerous calls to emergency management agencies from the public about which is the correct level. We are at Alert Level Two”Volcano Advisory.
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