Deep Earthquakes beneath Mount St. Helens: Evidence for Magmatic Gas Transport?

Small-magnitude earthquakes began beneath Mount St. Helens 40 days before the eruption of 20 March 1982. Unlike earlier preeruption seismicity for this volcano, which had been limited to shallow events (less than 3 kilometers), many of these earthquakes were deep (between 5 and 11 kilometers). The l...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1983-09, Vol.221 (4618), p.1391-1394
Main Authors: Weaver, Craig S., Zollweg, James E., Malone, Stephen D.
Format: Article
Language:English
Subjects:
Earthquakes
Explosives
Fluid pressure
Gas transport
Impact craters
Magma
Observations
Oil pools
Seismic energy
Seismological research
Volcanic activity prediction
Volcanic domes
Volcanoes
Volcanological research
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Summary:Small-magnitude earthquakes began beneath Mount St. Helens 40 days before the eruption of 20 March 1982. Unlike earlier preeruption seismicity for this volcano, which had been limited to shallow events (less than 3 kilometers), many of these earthquakes were deep (between 5 and 11 kilometers). The location of these preeruptive events at such depth indicates that a larger volume of the volcanic system was affected prior to the 20 March eruption than prior to any of the earlier dome-building eruptions. The depth-time relation between the deep earthquakes and the explosive onset of the eruption is compatible with the upward migration of magmatic gas released from a separate deep reservoir.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.221.4618.1391