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  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (1)
  • friction, eartquake  (1)
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  • 1
    facet.materialart.
    Unknown
    Measuring fracture energy under coseismic conditions (2018)
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    Publication Date: 2018-03-07
    Description: Experiments performed on rocks at deformation conditions typical of seismic slip, show an extremely low friction coefficient, the activation of lubrication processes and a power-law strength decay from a peak value to a residual, steady-state value. The weakening curve has an initially very abrupt decay which can be approximated by a powerlaw. The resulting experimental fracture energy (defined, for a given slip amount u, as the integral between the frictional curve and the minimum frictional level reached σf (u)) scales on most of the slip range as G ∝ u α, a power-law in some aspects in agreement with the seismological estimates of G0 ∝ u 1.28 proposed by Abercrombie and Rice (2005). The values of G and G0 are comparable for slips of about u = 1cm (G ≈ 104 J/m2 ). Both gradually increase with slip up to about 106 J/m2, however, it appears that fracture energy G0 is slightly larger than G in the range of slip 0.1 〈 u 〈 10. The effective G0 observed at the seismological scale should implicitly incorporate energy sinks other than frictional dissipation alone, which we discuss (anelastic damage due to high off-fault dynamic stress close to the rupture tip; dissipation during slip-localizing process within fault gouge of finite thickness; strain accomodating fault roughness at different scales). Since G0 is obtained by estimating the amount of dissipation with respect to strain energy and radiated energy, it will implicitly incorporate the sum of all dissipative processes due to rupture propagation and fault slip. From the comparison of G obtained in the lab and in earthquakes, it appears that friction alone explains most of the dissipation, except maybe at the larger magnitudes
    Description: Published
    Description: Vienna
    Description: 2T. Sorgente Sismica
    Keywords: friction, eartquake
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 2
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    Unknown
    Earthquake fault dynamics: Insights from laboratory experiments (2011)
    Details
    Publication Date: 2020-02-24
    Description: The determination of rock friction under the conditions of seismic slip in the Earth crust (slip rates of the order of 1 m/s or more and normal stress of hundreds of MPa) is of paramount importance in earthquake mechanics. Fault friction controls the stress drop, the mechanical work and the frictional heat generated during the slip. However the essential engine of earthquakes is buried at several kilometers depth and only remote, indirect measurements, which are not sufficient to fully characterize fault dynamics, are available. Elucidating constraints are derived from experimental studies performed in powerful apparatuses applying rotary shear motion to rock samples. The experiments indicate that when slip velocities and normal stresses approach those of actual earthquakes, a significant decrease in friction kicks-in (of up to one order of magnitude), which we term fault lubrication, both for cohesive rocks (silicate-built, quartz-built and carbonate-built) and non-cohesive rocks (clay-rich, anhydrite, gypsum and dolomite gouges) typical of crustal seismogenic sources. The available mechanical work and the associated temperature rise in the slipping zone trigger a number of physicochemical processes (gelification, decarbonation and dehydration reactions, melting and so on) whose products are responsible for fault lubrication.
    Description: European Research Council
    Description: Published
    Description: l'Aquila, Italia
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: open
    Keywords: friction ; experiments ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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