Mount St. Helens, Washington
Summary of Mount St. Helens Seismic Activity,
August 1996


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 August 1996. Seventeen earthquakes were recorded beneath the volcano during the month. None of these earthquakes exceeded magnitude 2.0. A magnitude 1.7 event on August 28th was the largest earthquake beneath the volcano since February 1996. The number of earthquakes per month since January 1996 has fluctuated between 10 and 19. Activity at the volcano remains at a safe, background level.

Caption: Cross-sectional view showing the locations of earthquakes beneath Mount St. Helens during August 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 September 1, 1995 to August 31, 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.