USGS/Cascades Volcano Observatory, Vancouver, Washington
Mount St. Helens, Washington -
Summary of Mount St. Helens Volcanic Activity, November 1997
The following information is provided by the U.S. Geological
Survey's Cascades Volcano Observatory and by the
University of Washington's Geophysics Program.
The U.S. Geological Survey and University of Washington monitor
earthquakes and other activity at Mount St. Helens as part of the
USGS Volcano Hazards Program.
There were 54 well-located (quality BB or better) events at Mount St. Helens
last month. Of these, 25 had magnitudes >0.0 (46% of all earthquakes), with
the largest a M 2.0. For reference, October had 42 events, 12 of which
had M >0.0 (28% of earthquakes). The cumulative seismic energy expended
during November was less than in September 1997.
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[Map,11K,GIF]
Mount St. Helens Seismicity - Map and Cross-Section
Cross-sectional view showing the locations of earthquakes beneath Mount St.
Helens during November 1997. The cross-section represents a vertical slice
of the crust downward from line A-A' in the map view. The earthquakes
occurred in and around the magma conduit system that leads from the magma
reservoir to the dome. In this graph, 0 depth is referenced to 1.5 km
(about 1 mile) below the current summit of Mount St. Helens (8,363 feet
above sea level).
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[Map,9K,GIF]
Mount St. Helens Seismicity - Time vs. Depth
Graph showing relationship between time and depth of earthquakes beneath
Mount St. Helens from
December 1, 1996 to November 30, 1997.
In this graph, 0 depth is referenced to 1.5 km (about 1
mile) below the current summit of Mount St. Helens (8,363 feet above sea
level).
For More Information:
Link to:
Mount St. Helens Seismicity Information
-- Link courtesy
University of Washington Geophysics Program
URL for CVO HomePage is:
<http://vulcan.wr.usgs.gov/home.html>
URL for this page is:
<http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/1997/summary_nov97.html>
If you have questions or comments please contact:
<GS-CVO-WEB@usgs.gov>
12/05/97, Lyn Topinka