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

Journal of Volcanology and Geothermal Research

By:
, , and
DOI: 10.1016/j.jvolgeores.2010.08.015

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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