HR: 0800h
AN: V21C-0613    [Abstracts]
TI: Source Location of Explosive Activity of Tungurahua Volcano, Ecuador
AU: * Ruiz, M C
EM: mruiz@email.unc.edu
AF: University of North Carolina, 3315 Mitchell Hall, Chapel Hill, NC 27599 United States
AU: * Ruiz, M C
EM: mruiz@email.unc.edu
AF: Instituto Geofisico EPN, Ladron de Guevara s/n, Quito, 17-01 Ecuador
AU: Lees, J M
EM: jonathan_lees@unc.edu
AF: University of North Carolina, 3315 Mitchell Hall, Chapel Hill, NC 27599 United States
AU: Johnson, J B
EM: jeff.johnson@unh.edu
AF: University of New Hampshire, James Hall, Durham, NH 03824 United States
AB: During Tungurahua's fifth recent eruptive cycle, three temporary seismic and infrasonic stations were installed around the volcano at distances 3.5- 13 km from the active crater. More than 2,000 degassing events were recorded during a 43 day experiment in summer 2004. Events were classified as explosions, jetting tremors, and chugging sequences, according to waveform characteristics of infrasound records. The largest activity is marked by the occurrence of more than 75 explosion events per day. This activity peak was preceded by an increase in the occurrence of jetting tremors. Pressure amplitudes of explosion events span three orders of magnitude from 0.1 to 180 Pa at the closest station with a power-law amplitude distribution. Explosion events with largest degassing rates occurred mainly at the beginning and at the end of the explosive phase. Waveform analysis of infrasound signals generated by explosion events reveals the presence of at least four families of events, although most of the signals can not be grouped in characteristic clusters. Using delay times between seismic and infrasonic signals at the three stations located on the volcano edifice, we constrain Tungurahua's explosion sources to depths shallower than 200 m below the crater floor. Projections of particle motions of seismic signals at different azimuths pinpoint the explosion source around the crater area. Attenuation profiles of acoustic waveforms further support a shallow source located close to the vent.
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005