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Publication Detail
Laboratory measurements of the physical properties of Triassic Evaporites from Central Italy and correlation with geophysical data
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Article
  • Authors:
    Trippetta F, Collettini C, Vinciguerra S, Meredith PG
  • Publisher:
    ELSEVIER SCIENCE BV
  • Publication date:
    20/09/2010
  • Pagination:
    121, 132
  • Journal:
    TECTONOPHYSICS
  • Volume:
    492
  • Issue:
    1-4
  • Print ISSN:
    0040-1951
  • Language:
    EN
  • Keywords:
    Physical properties, Evaporites, Laboratory measurements, Vp/Vs ratio, Seismic properties, Permeability, KOLA SUPERDEEP WELL, NORMAL-FAULT SYSTEM, NORTHERN APENNINES, P-WAVE, CAJON PASS, VELOCITY ANISOTROPY, COMPRESSIONAL WAVES, SEISMIC PROPERTIES, MECHANICAL MODEL, FLUID PRESSURE
  • Addresses:
    Trippetta, F
    Univ Perugia
    Dipartimento Sci Terra
    I-06123
    Perugia
    Italy
Abstract
The Triassic Evaporites (TE) of the Umbria-Marche Apennines, a sedimentary succession made up of a sequence of alternating sulphates (anhydrites and gypsum) and dolostones, represent a key lithology in terms of sealing properties and earthquake triggering. Here we: (1) report laboratory measurements of density, porosity, Vp. Vs, seismic anisotropy and permeability at effective confining pressures from 0 to 100 MPa, conducted on samples of TE collected from both outcrops and boreholes; and (2) attempt to upscale the laboratory results to larger scale geophysical investigation, such as Vp sonic logs, seismic tomography and in situ measurements of pore-fluid pressure. The average laboratory P-wave velocity is 6.0 km/s for dolostones, 4.6 km/s for gypsum-dolostones and 5.8 km/s for anhydrites, at ambient pressure. As effective confining pressure is increased up to 100 MPa, the average P-wave velocity increases to 7.0 km/s for dolostones, 5.3 km/s for gypsum and 6.4 km/s for anhydrites. Vp/Vs ratios appear to be independent of confining pressure, with average values of similar to 1.8 to similar to 2.2 for sulphates and similar to 1.9 to similar to 2.2 for dolostones, respectively, for dry and saturated conditions. All samples are characterized by very low permeability (10(-18) m(2) to 10(-21) m(2)), with the higher values for gypsum-dolostones and fractured dolostones samples. The Vp profiles obtained from ultrasonic laboratory measurements match well the in situ Vp profiles measured using sonic logs. In the laboratory, the Vp/Vs ratio increases when pressurized pore fluids are present, in agreement with 4D seismic tomography that relates the increase in Vp/Vs ratio to the migration of fluids during the 1997 Umbria-Marche seismic sequence (M-max similar to 6.0) that nucleates within the TE. Our low-permeability values are consistent with deep borehole measurements of high pore-fluid pressure trapped within the Triassic Evaporites. (C) 2010 Elsevier B.V. All rights reserved.
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