The missing sinks: Slip localization in faults, damage zones, and the seismic energy budget

Shipton, Zoe K.; Evans, James P.; Abercrombie, Rachel E.; Brodsky, Emily E.

doi:10.1029/170gm22

Cited by 43 publications

(50 citation statements)

References 32 publications

(44 reference statements)

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“…For a given rock type, seismic velocity and Poisson's ratio vary significantly with crack density (Walsh 1965;Kachanov 1986). The crack density is much higher on or near the fault than around it (Shipton et al 2006), leading to velocity contrasts of 5-15% at typical earthquake nucleation depths (Ben-Zion et al 2007). This is consistent with a softening of K C relative to K L (of the order of 10-32%), providing a mechanism for reducing β in the approach to the MEP solution, and moving the system away from the strict critical point.…”

Section: Discussionsupporting

confidence: 58%

Entropy production and self-organized (sub)criticality in earthquake dynamics

Main

Naylor

2010

Phil. Trans. R. Soc. A.

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We derive an analytical expression for entropy production in earthquake populations based on Dewar's formulation, including flux (tectonic forcing) and source (earthquake population) terms, and apply it to the Olami-Feder-Christensen numerical model for earthquake dynamics. Assuming the commonly observed power-law rheology between driving stress and remote strain rate, we test the hypothesis that maximum entropy production (MEP) is a thermodynamic driver for self-organized 'criticality' (SOC) in the model. MEP occurs when the global elastic strain is near-critical, with small relative fluctuations in macroscopic strain energy expressed by a low seismic efficiency, and broad-bandwidth power-law scaling of frequency and rupture area. These phenomena, all as observed in natural earthquake populations, are hallmarks of the broad conceptual definition of SOC (which has, to date, often included self-organizing systems in a near but strictly subcritical state). In the MEP state, the strain field retains some memory of past events, expressed as coherent 'domains', implying a degree of predictability, albeit strongly limited in practice by the proximity to criticality and our inability to map the natural stress field at an equivalent resolution to the numerical model.

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Section: Discussionsupporting

confidence: 58%

Entropy production and self-organized (sub)criticality in earthquake dynamics

Main

Naylor

2010

Phil. Trans. R. Soc. A.

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“…All the energy dissipation occurs on the fault plane. In contrast, real faults involve energy dissipation in a volume surrounding the fault through grain crushing, off-fault cracking etc [Shipton et at, 2006a;Cocco et at, 2006]. In theory, this situation can be accommodated in the theoretical model if we introduce multiple faults.…”

Section: Theoretical Model Vs Real Faultsmentioning

confidence: 99%

Energy partitioning during an earthquake

Kanamori

Rivera

2006

Geophysical Monograph Series

176

152

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We investigate the partitioning of energy released during an earthquake to radiated, fracture and thermal energies in an attempt to link various observational results obtained in different disciplines. The fracture energy, E G , used in seismology is different from that commonly used in mechanics where it is the energy used to produce new crack surface. In the seismological language it includes the energies used for off-fault cracking, and various thermal processes. The seismic moment, M o ' the radiated energy, E R , and rupture speed, V R , are key macroscopic parameters. The static stress drop can be a complex function of space, but if an average can be defined as f11, it is also a useful source parameter. From the combination of M o ' E R , and, f11 we can estimate the radiation efficiencY11R' or EG which can also be estimated independently from V R . 11R provides a link to the results of dynamic modeling of earthquakes which determines the displacement and stress on the fault plane. Theoretical and laboratory results can also be compared with earthquake data through 11K Also, the fracture energy estimated from the measurement of the volume and grain size of gouge of an exhumed fault can be linked to seismic data through 11K In these comparisons, the thermal energy is not included, and it must be estimated independently from estimates of sliding friction during faulting. One of the most challenging issues in this practice is how to average the presumably highly variable slip, stress and frictional parameters to seismologically determinable parameters.

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“…Shallow faults sharply cut pristine rocks, hard soils, and young tuffs [e.g., Evans and Bradbury, 2007]. Deep faults often nucleate from preexisting weaknesses [e.g., Shipton et al, 2006aShipton et al, , 2006b]. Still some parts of deep fault surfaces must penetrate fresh rock at the start of their histories.…”

Section: Application To Shallow and Pristine Rockmentioning

confidence: 99%

“…This note examines why strain and strain rate localize to a width that is miniscule compared to the depth and lateral extent of fault zones and the effects of dynamic weakening mechanisms. I acknowledge that this situation is not universal and that classes of exhumed faults with less strain localization are well documented [e.g., Shipton et al, 2006aShipton et al, , 2006b]. …”

Section: Introductionmentioning

confidence: 99%

Application of rate and state friction formalism and flash melting to thin permanent slip zones of major faults

Sleep

2010

Geochem Geophys Geosyst

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[1] Strain within certain major exhumed fault zones concentrated within a ∼1 mm wide permanent slip zone. A surrounding 10 mm thick fault core is strongly damaged. Concentration of seismic strain rate within a very thin zone is expected both for rate and state friction and weakening of the slip zone by flash melting at real contacts. In both cases, the material at the rupture tip begins with a strength that is far above that for steady state sliding. The permanent slip zone is slightly weaker than its surroundings and begins to slip with a strain rate faster than the surrounding core. Damage from strain thus weakens the sliding zone more than the fault core further concentrating strain rate toward a minimum thickness that depends on the finite size of grains. Flash heating involves a weakening velocity that is the product of a material property, the weakening strain rate, and the slip zone thickness. There is a minimum strength associated with a sliding velocity ∼15 m s , where stresses at the crack tip just exceed the elastic limit. Higher sliding velocities imply large inelastic strains near the rupture tip that would add to macroscopic friction. Lower sliding velocities imply higher coefficients of friction, as flash weakening is velocity weakening. The width of the PSZ should organize to a finite value so its weakening velocity is that needed to give the sliding velocity for minimum strength.Components: 9000 words, 5 figures.

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The missing sinks: Slip localization in faults, damage zones, and the seismic energy budget

Cited by 43 publications

References 32 publications

Entropy production and self-organized (sub)criticality in earthquake dynamics

Entropy production and self-organized (sub)criticality in earthquake dynamics

Energy partitioning during an earthquake

Application of rate and state friction formalism and flash melting to thin permanent slip zones of major faults

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