Temporal changes in stress preceding the 2004-2008 eruption of Mount St. Helens, Washington

Journal of Volcanology and Geothermal Research
By: , and 

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Abstract

The 2004-2008 eruption of Mount St. Helens (MSH), Washington, was preceded by a swarm of shallow volcano-tectonic earthquakes (VTs) that began on September 23, 2004. We calculated locations and fault-plane solutions (FPS) for shallow VTs recorded during a background period (January 1999 to July 2004) and during the early vent-clearing phase (September 23 to 29, 2004) of the 2004-2008 eruption. FPS show normal and strike-slip faulting during the background period and on September 23; strike-slip and reverse faulting on September 24; and a mixture of strike-slip, reverse, and normal faulting on September 25-29. The orientation of ??1 beneath MSH, as estimated from stress tensor inversions, was found to be sub-horizontal for all periods and oriented NE-SW during the background period, NW-SE on September 24, and NE-SW on September 25-29. We suggest that the ephemeral ~90?? change in ??1 orientation was due to intrusion and inflation of a NE-SW-oriented dike in the shallow crust prior to the eruption onset. ?? 2010 Elsevier B.V.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Temporal changes in stress preceding the 2004-2008 eruption of Mount St. Helens, Washington
Series title Journal of Volcanology and Geothermal Research
DOI 10.1016/j.jvolgeores.2010.08.015
Volume 198
Issue 1-2
Year Published 2010
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Volcanology and Geothermal Research
First page 129
Last page 142