This research is to investigate the implications of a new, unusually long (at least two hours) seismic wave train having periods of about 230 sec that was recorded at seismic stations throughout the world following the major eruption of Mount Pinatubo in the Philippines on June 15, 1991. Preliminary analysis indicates that this was a Rayleigh wave excited by atmospheric oscillations near the volcano that were set off by continuous thermal energy flux from the volcano. If this conclusion is correct, one can expect similar oscillations for other eruptions observed on the new NSF-supported Global Seismic Network (GSN). Acoustically coupled Rayleigh waves can be used for detection, characterization and quantification of major volcanic eruptions and for study of the properties of the Earth's atmosphere. A quantitative description of the source is desirable as it would allow us to estimate the amount of material injected in to the atmosphere which in turn permits us to estimate the general impact on the environment. Volcanic plumes pose a particular threat to air traffic and the seismic signal emitted by large volcanic eruptions has the potential to yield rapid estimates about the plume dimensions.
