Mount St. Helens, Washington
Summary of Mount St. Helens Seismic Activity,
April 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 April 1996. Sixteen earthquakes were recorded during the month, compared to 17 earthquakes the previous month. None of the April earthquakes exceeded magnitude 2.0; most were smaller than magnitude 0.0. There were no explosions or unusual rockfalls or avalanches in the crater during April. Activity at the volcano remains at a safe, background level.

Graphic

Caption: Cross-sectional view showing the locations of earthquakes beneath Mount St. Helens during April 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.

Graphic

Caption: Graph showing relationship between time and depth of earthquakes beneath Mount St. Helens from May 1, 1995 to April 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.