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Lamb pulse observed in nature

Kanamori, Hiroo and Given, Jeffrey W. (1983) Lamb pulse observed in nature. Geophysical Research Letters, 10 (5). pp. 373-376. ISSN 0094-8276. doi:10.1029/GL010i005p00373.

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Seismograms observed at Longmire, Washington, for four eruptions of Mt. St. Helens (May 18, June 13, August 7, and August 8, 1980), can be interpreted as Lamb pulses excited by a nearly vertical single force that represents the counter force of the eruption. These data provide reliable estimates of the impulse of the force K (time integral of the force) from which the total momentum and the kinetic energy, E, of the ejecta associated with the eruption can be estimated. The values of K are estimated to be 1.4 × 10^(19), 1.4 × 10^(16), 3.7 × 10^(15), and 2.8 × 10^(15) dyne·s for the four eruptions (chronological order), respectively. The corresponding values of E are estimated to range from 0.70 to 2.6 × 10^(23), 0.70 to 2.6 × 10^(20), 1.9 to 6.9 × 10^(19), and 1.4 to 5.3 × 10^(19) ergs using values of ejecta velocity ranging from 100 to 375 m/s. The ratio of K to the amplitude of the air wave excited by the eruption is 20 to 40 times larger for the main event on May 18 than for the other events suggesting a significant difference in the eruptive mechanism. Our results demonstrate that a digital seismograph in the vicinity of volcanoes provides a simple means for quantification of the explosive power of a volcanic eruption.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:Copyright 1983 by the American Geophysical Union. (Received November 16, 1982; revised February 16, 1983; accepted February 22, 1983.) Paper number 3L0352. We thank Robert Engdahl and John Hoffman for providing us with the LON digital seismogram tapes used in this study. Tom McEvilly gave us useful data necessary for computing the response of the DWWSSN instrument to air-waves. This research was partially supported by National Aeronautics and Space Administration grant number NSG-7610, and National Science Foundation grant EAR811-6023. Contribution No. 3843, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
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Caltech Division of Geological and Planetary Sciences3843
Issue or Number:5
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Official Citation:Hiroo Kanamori and Jeffrey W. Given (1983), Lamb pulse observed in nature. Geophysical Research Letters, 10: 373–376. doi: 10.1029/GL010i005p00373
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51047
Deposited By: George Porter
Deposited On:30 Oct 2014 16:59
Last Modified:10 Nov 2021 19:04

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