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Analysis of seismic body waves excited by the Mount St. Helens eruption of May 18, 1980Seismic body waves which were excited by eruption of Mt. St. Helens, and recorded by the Global Digital Seismographic Network (GDSN) stations are analyzed to determine the nature and the time sequence of the events associated with the eruption. The polarity of teleseismic P waves (period 20 sec) is identical at six stations which are distributed over a wide azimuthal range. This observation, together with a very small S to P amplitude ratio (at 20 sec), suggests that the source is a nearly vertical single force that represents the counter force of the eruption. The time history of the vertical force suggests two distinct groups of events, about two minutes apart, each consisting of several subevents with a duration of about 25 sec. The magnitude of the force is approximately 2.6 to the 17th power dyne. This vertical force is in contrast with the long period (approximately 150 sec) southward horizontal single force which was determined by a previous study and interpreted to be due to the massive landslide. Previously announced in STAR as N83-15968
Document ID
19840057219
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kanamori, H.
(California Inst. of Tech. Pasadena, CA, United States)
Given, J. W.
(California Inst. of Tech. Pasadena, CA, United States)
Lay, T.
(California Institute of Technology Pasadena, CA, United States)
Date Acquired
August 12, 2013
Publication Date
March 10, 1984
Publication Information
Publication: Journal of Geophysical Research
Volume: 89
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
84A40006
Funding Number(s)
CONTRACT_GRANT: NSF EAR-81-16023
CONTRACT_GRANT: NSG-7610
Distribution Limits
Public
Copyright
Other

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