Analysis of seismic body waves excited by the Mount St. Helens eruption of May 18, 1980 ( USA).

Abstract

Seismic body waves which were excited by the May 18, 1980, eruption of Mount St. Helens and recorded by the Global Digital Seismographic Network stations are analyzed to determine the nature and the time sequence of the events associated with the eruption. Observations suggest that the source is a nearly vertical single force. A simple model shows that for seismic radiation a volcanic eruption can be represented by a single force applied in the direction opposite to the blast direction. The time history of the vertical force suggests two distinct groups of events, about 2 min apart, each consisting of several subevents with a duration of about 25s. -from Authors