HR: 1330h
AN: V23A-05    [Abstracts]
TI: Laboratory and Field Determination of Seismic Velocities at Campi Flegrei: a Joint Interpretation of Mechanical Features.
AU: Vinciguerra, S
EM: vinciguerra@ov.ingv.it
AF: Osservatorio Vesuviano-INGV, Via Diocleziano,328, Naples, 80124 Italy
AU: Trovato, C
EM: trovato@ov.ingv.it
AF: Osservatorio Vesuviano-INGV, Via Diocleziano,328, Naples, 80124 Italy
AU: Trovato, C
EM: trovato@ov.ingv.it
AF: D'Appolonia S.p.A., via S. Pasquale a Chiaia, 62, Naples, 80100 Italy
AU: Meredith, P
EM: meredith@ucl.uc.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E6BT United Kingdom
AU: Boon, S
EM: boon@ucl.uc.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E6BT United Kingdom
AU: Benson, P
EM: benson@ucl.uc.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E6BT United Kingdom
AU: * Troise, C
EM: claudia@ov.ingv.it
AF: Osservatorio Vesuviano-INGV, Via Diocleziano,328, Naples, 80124 Italy
AU: De Natale, G
EM: claudia@ov.ingv.it
AF: Osservatorio Vesuviano-INGV, Via Diocleziano,328, Naples, 80124 Italy
AU: Carlino, S
EM: stefanocarlino@mail.it
AF: D'Appolonia S.p.A., via S. Pasquale a Chiaia, 62, Naples, 80100 Italy
AU: Somma, R
EM: somma@katamail.it
AF: D'Appolonia S.p.A., via S. Pasquale a Chiaia, 62, Naples, 80100 Italy
AB: We present an interpretation of mechanical features of Campi Flegrei rocks as obtained by the joint consideration of laboratory measurements and of local earthquake tomography. We studied seismic velocities and permeabilities on Campi Flegrei caldera (Italy) tuffs. Measurements were made in a servo-controlled steady-state-flow permeameter at effective pressures from 5-80MPa, during both increasing and decreasing pressure cycles. Selected samples were thermally stressed at temperatures up to 600° C to induce thermal crack damage Acoustic emission output was recorded throughout each thermal stressing experiment. Campi Flegrei tuff is a strongly heterogeneous pyroclastic flow material, which includes cavities, pumice and crystals. It has an initial porosity of around 45%, and a P-wave velocities that increases from around 2 km/s to around 3 km/s over the pressure range 5 to 80 MPa. Significant velocity hysteresis was observed in the tuff, with only about 50% of the velocity change recovered during depressurization. The P and S velocities as measured in laboratory are very coherent with the results obtained in this work from local earthquake tomography. AE recorded during thermal treatment shows higher bursts of activity around 200-300° C and 500-600° C, further confirming that thermal cracking is a primary deformation mechanism too, acting by enhancing crack propagation and dehydration of the zeolite phases present. In order to model the deformation processes involving the Campi Flegrei area and further understand the relatiosnhips between stress and strain acting in the area, we measured elastic moduli and fracture parameters of Neapolitan Yellow and Mt. Epoemo Green Tuffs. Fracture parameters have been determined on the basis of the maximum compressional strength, obtained through stress-strain curves. Experimental work has been carried out with the facilites installed at the Laboratory of Rock Physics at OV-INGV.
DE: 5104 Fracture and flow
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5120 Plasticity, diffusion, and creep
DE: 7203 Body wave propagation
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly