ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks  (1)
  • 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability  (1)
  • 1
    facet.materialart.
    Unknown
    Physical and transport properties of isotropic and anisotropic cracked rocks under hydrostatic pressure (2007)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: A key consequence of the presence of microcracks within rock is their significant influence upon elastic anisotropy and transport properties. Here two rock types (a basalt and a granite) with contrasting microstructures, dominated by microcracks, have been investigated using an advanced experimental arrangement capable of measuring porosity, P wave velocity, S wave velocity, and permeability contemporaneously at effective pressures up to 100 MPa. Using the Kachanov (1994) noninteractive effective medium theory, the measured elastic wave velocities are inverted using a least squares fit, permitting the recovery of the evolution of crack density and aspect ratio with increasing isostatic pressure. Overall, the agreement between measured and predicted velocities is good, with average error less than 0.05 km/s. At larger scales and above the percolation threshold, macroscopic fluid flow also depends on the crack density and aspect ratio. Using the permeability model of Gue´guen and Dienes (1989) and the crack density and aspect ratio recovered from the elastic wave velocity inversion, we successfully predict the evolution of permeability with pressure for direct comparison with the laboratory measurements. We also calculate the evolution of the crack porosity with increasing isostatic pressure, on the basis of the calculated crack density, and compare this directly with the experimentally measured porosity. These combined experimental and modeling results illustrate the importance of understanding the details of how rock microstructures change in response to an external stimulus when predicting the simultaneous evolution of rock physical properties.
    Description: Published
    Description: B04202
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: open
    Keywords: microcracked ; rocks ; 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 2
    facet.materialart.
    Unknown
    Positive and negative feedback in the earthquake cycIe: the role of pore fluids on states of criticality in the crust (2006)
    Details
    Publication Date: 2019-11-04
    Description: Fluids exert a strong physical and chemical control on local processes of rock fracture and friction. For example they may accelerate fracture by stress corrosion reactions or the development of overpressure (a form of positive feedback), or retard fracture by time-dependent stress relaxation or dilatant hardening (negative feed-back), thereby introducing a variable degree of local force conservation into the process. In particular the valve action of dynamic faulting may be important in tuning the Earth to a metastable state of incipient failure on all scales over several cycles, similar to current models of Self-Organised Criticality (SOC) as a paradigm for eartiquakes However laboratory results suggest that ordered fluctuations about this state may occur in a single cycle due to non conservative processes involving fluids which have the potential to be recognised, at least in the short term, in the scaling properties of earthquake statistics. Here we describe a 2-D cellular automaton which uses local rules of positive and negative feedback to model the effect of fluids on failure in a heterogeneous medium in a single earthquake cycle. The model successfully predicts the observed fractal distribution of fractures, with a negative correlation between the predicted seismic b-value and the local crack extension force G. Such a negative correlation is found in laboratory tests involving (a) fluid-assisted crack growth in tension (b) water-saturated compressional deformation, and (c) in field results on an intermediate scale from hydraulic mining-induced seismicity all cases where G can be determined independently, and where the physical and chemical action of pore fluids is to varying degrees a controlled variable. For a finite local hardening mechanism (negative feedback), the model exhibits a systematic increase followed by a decrease in the seismic b-value as macroscopic failure is approached, similar to that found in water-saturated laboratory tests under controlled «undrained» conditions, and where dilatancy hardening is independently known to be a local mechanism of negative feedback. A similar pattern is suggested from selected field observations from natural seismicity, albeit with a lesser degree of statistical significance.
    Description: JCR Journal
    Description: open
    Keywords: self-organised criticality ; fractals ; fluid-rock interactions ; seismicity ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 6396760 bytes
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...