HR: 14:10h
AN: V52C-03    [PDF]
TI: Seismo-Acoustic Monitoring of the Dec. 2002 Eruption of Stromboli Volcano
AU: * Ripepe, M
EM: mripepe@geo.unifi.it
AF: Dip. Scienze della Terra, Universita' di Firenze, Via LaPira, 4, Firenze, 50121 Italy
AU: Marchetti, E
EM: marchetti@geo.unifi.it
AF: Dip. Scienze della Terra, Universita' di Firenze, Via LaPira, 4, Firenze, 50121 Italy
AU: Fiaschi, A
EM: fiaschi@igt.it
AF: Dip. Scienze della Terra, Universita' di Firenze, Via LaPira, 4, Firenze, 50121 Italy
AU: Ulivieri, G
EM: gulivieri@geo.unifi.it
AF: Dip. Scienze della Terra, Universita' di Firenze, Via LaPira, 4, Firenze, 50121 Italy
AB: On December 28, 2002, after several days of sustained strong explosive activity, an extremely fast lava flow run over the NE crater rim along the flank of Sciara del Fuoco partially filling the small basin at 650 m a.s.l. and reaching the sea in few minutes. A couple of days later, on December 30, with the lava still flowing out, a large landslide affected the subaerial and the underwater flank of the Sciara del Fuoco. The landslide produced tsunami waves which have severely damaged the San Vincenzo village and were observed all around the southern Tyrrhenian sea. The volcanic activity, following the landslide, was characterized by effusive activity from a lava field at 650 m, with no visible explosions from the summit crater. Since January 4, 2003 a seismo-acoustic network of 5 stations and a five-elements infrasonic array were deployed on the summit of Stromboli volcano. Each station consists on a 5 channel 16 bits A/D converter, a Guralp CMG-40T broadband seismometer and an infrasonic microphone. Digital data are radio-transmitted from the summit to the recording site in the village of Stromboli, at 9600 baud rate. Seismic activity during the effusive activity after the Dec. 30 landslide was characterized by a low amplitude tremor and by seismic transients with a clear VLP component (3-20 s) evidencing the internal magma dynamics. In spite of the absence of visible explosions at the craters, number of VLP per hour was high (10-15 events) and their waveform was typical of the pre-eruptive explosive activity. Location of the VLP after the eruption was not changed and remained stable indicating that source dynamics and conduit geometry were not affected by the collapse of the Sciara del Fuoco. This frequent seismic activity was seldom accompanied by weak (3-10 Pa) acoustic signals, revealed and located by the infrasonic array mainly in the NE crater. The presence of infrasound associated to seismic VLP indicated that the conduit were still opened and active even if the craters were thermically cold. However, the low infrasound and VLP amplitude was a clear evidence that the gas exsolved in the magmatic system and hence the explosive energy was reduced. This was also confirmed by the extremely large time delays (up to 30 s) between the seismic and acoustic onset. This general trend was interrupted by the strong April 5 explosion. After the minimum values recorded in May-June 2003, amplitude is now increasing toward the level of the typical strombolian explosive activity.
DE: 7280 Volcano seismology (8419)
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting