Mount St. Helens:
Summary of Mount St. Helens Seismic Activity,
March 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 March 1996. Seventeen earthquakes were recorded during the month, compared to 13 earthquakes the previous month. None of the March earthquakes exceeded magnitude 2.0. The rate of occurrence of earthquakes has remained relatively steady at a low level since December 1995. The current level of earthquake activity is similar to that during early 1995, before a flurry of increased activity from June to November 1995. There were no explosions or unusual rockfalls or avalanches in the crater during March. Activity at the volcano remains at a safe, background level.

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