HR: 0800h
AN: V11C-0745    [Abstracts]
TI: Observations of Cyclic Strombolian Eruptive Behavior at Fuego Volcano, Guatemala Reflected in the Seismo-Acoustic Record
AU: * Lyons, J J
EM: jlyons@mtu.edu
AF: Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AU: Johnson, J B
EM: jeff.johnson@ees.nmt.edu
AF: New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, United States
AU: Waite, G P
EM: gpwaite@mtu.edu
AF: Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AU: Rose, W I
EM: raman@mtu.edu
AF: Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AB: Fuego volcano is a high (3770m) basaltic cone which has been marked by >60 subplinian explosive eruptions and several year-long periods of nearly constant low level strombolian eruptions and lava flows. We have studied the current strombolian activity in detail to understand how a high cone erupts gas-rich basalt nearly continuously for many years. We compiled two years of observations of volcanic activity at Fuego in conjunction with digital seismo-acoustic recordings during a six month subset between January and July 2007. From visual observations we divide activity into three primary behaviors often occurring in a repeatable order starting with: 1) periods of lava effusion and subordinate strombolian explosions, followed by 2) paroxysmal, extended-duration, continuous strombolian emissions, and finally 3) periods of discrete degassing explosions with no lava effusion. The characteristic cycle of lava effusion, strombolian eruption, and degassing explosions repeated at least four times during the two-year study interval. Time durations of lava effusion and discrete explosive activity varied from weeks to months during 2005-2007, whereas the duration of the sustained strombolian eruptions were more consistently 24 to 48 hours. Our new seismic and acoustic data provide continuous records of eruptive behavior, which allow us to better quantify temporal duration and elucidate source processes associated with the various phases of the eruptive cycles. The seismo-acoustic station was located 7 km southwest of the active summit of Fuego, and included two infrasonic microphones and a 1 Hz short-period seismometer. These data are analyzed in conjunction with visual observations to identify spectral and amplitude characteristics of the three behaviors. For instance, we record relatively low amplitude acoustic and seismic signals and seismic tremor associated with lava effusion. We identify sustained strombolian eruptions with modulated tremor in both the seismic and acoustic wave fields. And we associate discrete degassing explosions possessing high amplitude acoustic waveforms and impulsive onsets with low amplitude seismic waveforms dominated by the ground-coupled airwave.
DE: 7280 Volcano seismology (8419)
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8419 Volcano monitoring (7280)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting