Ground-coupled acoustic airwaves from Mount St. Helens provide constraints on the May 18, 1980 eruption

Earth and Planetary Science Letters
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Abstract

The May 18, 1980 Mount St. Helens eruption perturbed the atmosphere and generated atmosphere-to-ground coupled airwaves, which were recorded on at least 35 seismometers operated by the Pacific Northwest Seismograph Network (PNSN). From 102 distinct travel time picks we identify coherent airwaves crossing Washington State primarily to the north and east of the volcano. The travel time curves provide evidence for both stratospheric refractions (at 200 to 300 km from the volcano) as well as probable thermospheric refractions (at 100 to 350 km). The very few first-hand reports of audible volcano sounds within about 80 km of the volcano coincide with a general absence of ground-coupled acoustic arrivals registered within about 100 km and are attributed to upward refraction of sound waves. From the coherent refracted airwave arrivals, we identify at least four distinct sources which we infer to originate 10 s, 114 s, ∼ 180 s and 319 s after the onset of an 8:32:11 PDT landslide. The first of these sources is attributed to resultant depressurization and explosion of the cryptodome. Most of the subsequent arrivals also appear to be coincident with a source located at or near the presumed volcanic conduit, but at least one of the later arrivals suggests an epicenter displaced about 9 km to the northwest of the vent. This dislocation is compatible with the direction of the sector collapse and lateral blast. We speculate that this concussion corresponds to a northern explosion event associated with hot cryptodome entering the Toutle River Valley.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Ground-coupled acoustic airwaves from Mount St. Helens provide constraints on the May 18, 1980 eruption
Series title Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2007.03.001
Volume 258
Year Published 2007
Language English
Publisher Elsevier
Publisher location Amsterdam
Contributing office(s) Volcano Hazards Program
Description 16 p.
First page 16
Last page 31
Country United States
State Washington
County Skamania County
Online Only (Y/N) N
Additional Online Files (Y/N) N