HR: 0800h
AN: S11B-0173    [Abstracts]
TI: Evidence of Velocity Variations During the Recent Mt. Etna Eruptive Activity Detected by Temporal Seismic Tomography
AU: Barberi, G
EM: barberi@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, 2 Piazza Roma, Catania, 95123 Italy
AU: Zhang, H
EM: hjzhang@geology.wisc.edu
AF: University of Wisconsin-Madison, Department of Geology and Geophysics, 1215 W. Dayton St., Madison, WI 53706 United States
AU: Cocina, O
EM: cocina@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, 2 Piazza Roma, Catania, 95123 Italy
AU: * Patanè, D
EM: patane@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, 2 Piazza Roma, Catania, 95123 Italy
AU: Thurber, C H
EM: thurber@geology.wisc.edu
AF: University of Wisconsin-Madison, Department of Geology and Geophysics, 1215 W. Dayton St., Madison, WI 53706 United States
AB: After nearly 10 years without any major flank eruption, volcanic activity resumed at Mt. Etna on July 17, 2001, giving rise to the first of the two most striking flank eruptions on this volcano in recent times. Fifteen months after the end (August 09, 2001) of this eruptive episode, a new eruption started abruptly on October 26, 2002 with only a few hours of premonitory seismicity accompanying the opening of eruptive fissures along a bi-radial direction. Since the end of this last eruption (January 2003), a period of weak volcanic activity occurred. On September 7, 2004 a new eruption occurred along a WNW-ESE to NW-SE oriented fracture system at the base of the South East summit crater. Compared to the previous two flank eruptions, the 2004 eruption did not have any measurable short-period seismicity and deformation variations. Since 2001, Mt. Etna is well covered by the INGV-CT permanent network and some temporary networks. This provides a unique opportunity to investigate seismic velocity variations before, during and after the three most recent eruptions. Characterizing spatial and temporal variations in seismic velocity in detail will yield a better understanding of the complex plumbing system beneath Mt. Etna and the triggering mechanisms for each eruption. The conventional way to detect temporal velocity changes is to separately invert velocity models for each data set and then examine their differences. This may, however, cause some artifacts in the velocity changes due to different data quality and distribution. Here we present a true temporal seismic tomography algorithm by constraining velocity models for different periods through a temporal smoothing operator. This technique considers the fact that the main features of the velocity models for different periods are similar. The temporal seismic tomography algorithm is based on the double-difference tomography code tomoDD that uses both absolute and differential arrival times to simultaneously determine event locations and the velocity model. Our preliminary results show that both Vp and Vs decrease underneath the central crater at depths of 0-5 km from the 2001 eruption to the 2002-2003 eruption, which may be related to the higher gas content of the magma intruded before the 2002-2003 eruption.
DE: 7270 Tomography (6982, 8180)
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
SC: Seismology [S]
MN: Fall Meeting 2005