Spurr volcano (United States) - Smithsonian / USGS Weekly Volcanic Activity Report for 21 July-27 July 2004 (New Activity / Unrest)
Wed, 21 Jul 2004, 06:00 | BY: VN
AVO raised the Concern Color Code at Spurr from Green to Yellow on 26 July after an increase in seismicity was recorded beneath the volcano's summit. Some earthquakes were interpreted to reflect the beginning stages of volcanic unrest. AVO noted that there were no indications that an eruption was imminent and that this type of seismicity can decline without leading to an eruption. Retrospective analysis suggested that the seismic increase began slowly, perhaps as early as February 2004. As of 26 July, the seismic network recorded 15-20 earthquakes daily. This rate was greater than any observed since the last eruptive period in 1992.
All earthquakes were less than magnitude 1.5 and ranged in depth between 1 and 6 km below sea level. Relatively few earthquakes were located beneath the Crater Peak vent, the site of the 1953 and 1992 eruptions. On 11 July a pilot reported a strong sulfur smell from Spurr and a new area of steaming, but AVO scientists observed neither during an overflight on 15 July.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
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From: Global Volcanism Program, 2004. Report on Spurr. In: Mayberry, G (ed.), Weekly Volcanic Activity Report 21 July-27 July 2004. Smithsonian Institution and US Geological Survey.
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