HR: 1330h
AN: S22B-0447    [PDF]
TI: 3-D Attenuation Structure of Mt. Etna Volcano
AU: Martinez-Areval, C
EM: carmara@ugr.es
AF: Instituto Andaluz de Geofisica. Universidad de Granada, Campus de Cartuja s/n, Granada, 18071 Spain
AU: * Rietbrock, A
EM: ariet@liverpool.ac.uk
AF: Department of Earth Sciencies. University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AU: Marrero, I
EM: ijmh40@tid.es
AF: Grupo TECNOBIT, Avda. de Europa, n§21, Alcobendas, 28108 Spain
AU: Almendros, J
EM: alm@iag.ugr.es
AF: Instituto Andaluz de Geofisica. Universidad de Granada, Campus de Cartuja s/n, Granada, 18071 Spain
AU: Patane, D
EM: patane@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia. Sezione di Catania, Piazza Roma, 2, Catania, 95125 Italy
AU: Ferrari, F
EM: ferrari@ct.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia. Sezione di Catania, Piazza Roma, 2, Catania, 95125 Italy
AU: Ibanez, J
EM: ibanez@iag.ugr.es
AF: Instituto Andaluz de Geofisica. Universidad de Granada, Campus de Cartuja s/n, Granada, 18071 Spain
AB: Seismic attenuation at Mt. Etna volcano has been studied in the last two decades using different methods and waves types. Only global attenuation properties of the etnean region are characterised in these studies. All of them corroborate that attenuation is stronger at low frequencies than at high frequencies, and that anelastic processes prevail over scattering. However, the details of the tridimensional (3-D) attenuation structure of Etna were not known. In this work, we perform an attenuation tomography of the shallow structure (depth less than 3 km b.s.l.). We apply a spectral inversion technique to the P-wave spectra, which constitutes a modification of the velocity tomography technique. We selected the spectra of 266 earthquakes belonging to the seismic swarm that marked the onset of the 2001 July eruption of Etna. The velocity model used to perform the attenuation tomography was obtained by PatanŠ et al. (2002). This velocity model has been also used to relocate the selected events. We assume an homogeneous initial attenuation model (1/Q=0.013), a damping value of 0.003, and a grid cell size of 2x2x1 km. The procedure has been verified with different synthetic resolution tests. The final model shows an aseismic body with low attenuation (1/Q$<$0.005) at a depth of 2 km b.s.l. and at 6 km from south of Central Craters (C.C.) zone. When the depth decreases, the attenuation increases in this area and it reaches the greatest values (1/Q$>$0.05) in the shallower layers (betwen 2 and 1 km a.s.l. If we compare the P-wave attenuation structure with the P-wave velocity and vP/vS structure (PatanŠ et al., 2002), we observe: a) at 1km b.s.l. and east from Bove Valley, there is a body with low vP/vS ratio and high P-wave attenuation; b) at sea level and at south from C.C. area, the P-wave velocity and attenuation are high and it is founded low vP/vS values, while in the Bove Valley, the vP/vS ratio is high and c) at 1 km a.s.l., the area at southwest from C.C. zone has low vP/vS values and high attenuation. However, in the Bove Valley, the attenuation is low and the vP/vS ratio is high.
DE: 5144 Wave attenuation
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting