The EarthScope Plate Boundary Observatory (PBO) Response Mt. St. Helens' 2004 Volcanic Crisis Abstract

abstract

  • Starting on September 23, 2004, the level of seismic activity at Mt. St. Helens increased to well above background levels. The majority of seismic activity was occurring at less than 1 kilometer depth under the lava dome that formed between 1980 and 1986. Seismic activity again increased significantly between September 26-29 with earthquakes occurring at about four per minute, with the largest events becoming more frequent and approaching Mw 2.5. In response to this increased level of activity, a PBO Standing Committee and Magmatic Systems Site Selection Working Group requested reprioritization and immediate installation of five PBO permanent GPS stations on and around the flanks of Mt. St. Helens to monitor deformation associated with this volcanic crisis. Twelve stations had been scheduled for installation in the summer of 2005 and fortunately site reconnaissance had been completed for these stations in the July of 2004. The PBO Permitting Coordinator worked closely with National Forest Service and USGS personnel to secure permits and permission for rapid installation of five stations. Field crews reached the volcano on October 12, 2004 and began assembly of a modified structure that holds solar panels and battery and equipment enclosures. Each enclosure was slung by helicopter to a site where a GPS antenna and radome were fixed to existing EDM towers. Four sites were completed in two days and the fifth site is scheduled for installation as soon as weather permits. The PBO Data Management and IT Group responded quickly to a request by USGS personnel that data downloads occur once per hour rather than once every 24 hours. Both hourly and daily data files are freely available through the UNAVCO Archive at ftp://data-out.unavco.org/pub/PBO_rinex.

publication date

  • 2004

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