John A. Power (Former Employee)

Airborne surveillance of gas emissions from Augustine Volcano and other Cook Inlet volcanoes began in 1990 to identify baseline emission levels during noneruptive conditions. Gas measurements at Augustine for SO2, CO2, and H2S showed essentially no evidence of anomalous degassing through spring 2005. Neither did a measurement on May 10, 2005, right after the onset of low level seismicity...

The 2005–6 eruption of Augustine Volcano produced tephra-fall deposits during each of four eruptive phases. Late in the precursory phase (December 2005), small phreatic explosions produced small-volume, localized, mostly nonjuvenile tephra. The greatest volume of tephra was produced during the explosive phase (January 11–28, 2006) when 13 discrete Vulcanian explosions generated ash...

The 2006 eruption of Augustine Volcano, Alaska, generated more than 3,500 earthquakes in a month-long time frame bracketing the most explosive period of activity. We examine two quantitative tools that, in retrospective analysis, were excellent indicators of imminent eruption. The first tool, referred to as the frequency index (FI), is based on a simple ratio of high- and low-frequency...

A series of 13 explosive eruptions occurred at Augustine Volcano, Alaska, from January 11–28, 2006. Each lasted 2.5 to 19 minutes and produced ash columns 3.8 to 13.5 km above mean sea level. We investigated various parameters to determine systematic trends, including durations, seismic amplitudes, frequency contents, signal characteristics, peak acoustic pressures, ash column heights...

Clustered earthquakes located 25 km northeast of Augustine Volcano occurred more frequently beginning about 8 months before the volcano’s explosive eruption in 2006. This increase in distal seismicity was contemporaneous with an increase in seismicity directly below the volcano’s vent. Furthermore, the distal seismicity intensified penecontemporaneously with signals in geodetic data that...

We use seismic b-values to explore physical processes during the Augustine Volcano 2005–6 preeruptive earthquake swarm. The preeruptive earthquake swarm was divided into two parts: the “long swarm,” which extended from April 30, 2005, to January 10, 2006; and the "short swarm," which started 13 hours before the onset of explosive activity on January 11, 2006. Calculations of b-value for...