Publication Date:
2017-04-04
Description:
We report laboratory measurements of P- and S-wave velocities on samples of tuff from
Campi Flegrei (Italy), and a new tomographic velocity map of the Campi Flegrei caldera. Laboratory
measurements were made in a hydrostatic pressure vessel during both increasing and decreasing effective
pressure cycles. Selected samples were also thermally stressed at temperatures up to 600 C to induce
thermal crack damage. Acoustic emission output was recorded throughout each thermal stressing
experiment, and velocities were measured after thermal stressing. Laboratory P- and S-wave velocities are
initially low for the tuff, which has an initial porosity of 45%, but both increase by between 25 and 50%
over the effective pressure range of 5 to 80MPa, corresponding to a decrease of porosity of 70%. Marked
velocity hysteresis, due to inelastic damage processes, is also observed in samples subjected to a
pressurization-depressurization cycle. Tomographic seismic velocity distributions obtained from field
recordings are in general agreement with the laboratory measurements. Integration of the laboratory
ultrasonic and seismic tomography data indicates that the tuffs of the Campi Flegrei caldera can be water
or gas saturated, and shows that inelastic pore collapse and cracking produced by mechanical and thermal
stress can significantly change the velocity properties of Campi Flegrei tuffs at depth. These changes need
to be taken into account in accurately interpreting the crustal structure from tomographic data.
Description:
Published
Description:
2205-2221
Description:
JCR Journal
Description:
reserved
Keywords:
Laboratory P- and S-wave velocities
;
tomographic velocity map
;
mechanical and thermal stresses
;
04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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