The following information is provided by the U.S. Geological Survey's Cascades Volcano Observatory and by the University of Washington's Geophysics Program.
Earthquake activity beneath Mount St. Helens remained at a low level during November 1996. Only ten earthquakes were located beneath the volcano during the month, the largest of magnitude 0.0. This is the lowest monthly total so far this year, and is within the range considered to be a safe, background level. Two of the earthquakes in November had magnitudes less than -1.0, and so do not appear on the accompanying plots.
Caption: Cross-sectional view showing the locations of earthquakes beneath Mount St. Helens during November 1996. 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). Data and graph provided by the Geophysics Program, University of Washington.
Caption: Graph showing relationship between time and depth of earthquakes beneath Mount St. Helens from December 1, 1995 to November 30, 1996. 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). Data and graph provided by the Geophysics Program, University of Washington.
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. Information updates will be posted here during the first week of each month, or more often if conditions warrant.
[Graphic,10K,GIF]
[Graphic,10K,GIF]