A study of different fault slip modes governed by the gouge material composition in laboratory experiments

Kocharyan, G. G.; Новиков, В. А.; Остапчук, А. А.; Павлов, Д. В.

doi:10.1093/gji/ggw409

Cited by 31 publications

(15 citation statements)

References 34 publications

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“…When the shear stress in the contact area reaches its critical value, the contact fails and sharp slip of the movable block occurs. The detailed description of the spring-block facility and diagnostic equipment can be found in Kocharyan and Novikov (2016), Kocharyan et al (2017). This facility employs the system of electrical action on the fault area, which provides a simulation of electric current through the fault for a study of its possible triggering impact on the seismic process.…”

Section: Experimental Methodsmentioning

confidence: 99%

Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

et al. 2017

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Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current (DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density (10 -7 -10 -8 A/m 2 ) generated by the pulsed power systems at the epicenter depth (5-10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory ''earthquake'' triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory ''earthquake'' (sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98-0.99 of its critical value. The threshold of electric triggering action is about 20 A/m 2 that is 7-8 orders of magnitude higher than estimated electric current density for Bishkek test site (Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties.

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Section: Experimental Methodsmentioning

confidence: 99%

Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

et al. 2017

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“…Laboratory experiments indicate that heterogeneity can affect the mechanical response of a fault. Kocharyan et al (2016) found in laboratory experiments that the stress drop of slip transients depends on the proportion of materials mixed in a composite gouge. Ma and He (2001) found period doubling phenomena in experiments with two different materials along a frictional surface.…”

Section: Geological and Physical Backgroundmentioning

confidence: 99%

Stability of faults with heterogeneous friction properties and effective normal stress

2018

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Abundant geological, seismological and experimental evidence of the heterogeneous structure of natural faults motivates the theoretical and computational study of the mechanical behavior of heterogeneous frictional interfaces. Fault zones are composed of a mixture of materials with contrasting strength, which may affect the spatial variability of seismic coupling, the location of high-frequency radiation and the diversity of slip behavior observed in natural faults. To develop a quantitative understanding of the effect of strength heterogeneity on the mechanical behavior of faults, here we investigate a fault model with spatially variable frictional properties and pore pressure. Conceptually, this model may correspond to two rough surfaces in contact along discrete asperities, the space in between being filled by compressed gouge. The asperities have different permeability than the gouge matrix and may be hydraulically sealed, resulting in different pore pressure. We consider faults governed by rate-and-state friction, with mixtures of velocity-weakening and velocity-strengthening materials and contrasts of effective normal stress. We systematically study the diversity of slip behaviors generated by this model through multi-cycle simulations and linear stability analysis. The fault can be either stable without spontaneous slip transients, or unstable with spontaneous rupture. When the fault is unstable, slip can rupture either part or the entire fault. In some cases the fault alternates between these behaviors throughout multiple cycles. We determine how the fault behavior is controlled by the proportion of velocity-weakening and velocity-strengthening materials, their relative strength and other frictional properties. We also develop, through heuristic approximations, closed-form equations to predict the stability of slip on heterogeneous faults. Our study shows that a fault model with heterogeneous materials and pore pressure contrasts is a viable framework to reproduce the full spectrum of fault behaviors observed in natural faults: from fast earthquakes, to slow transients, to stable sliding. In particular, this model constitutes a building block for models of episodic tremor and slow slip events.Keywords: fault heterogeneity; heterogeneous pore-pressure; slip instability; earthquakes; rate-and-state friction; linear stability analysis Highlights:1. A comprehensive study of slip behaviors in fault models with mixed velocity-strengthening / velocity-weakening materials and heterogeneous effective normal stress 2. Fault stability investigated with numerical rate-and-state simulations and analytical linear stability analysis 3. Rich range of slip behaviors including steady-slip, slow aseismic slip transients, ruptures localized in part of the fault (P-instability), ruptures breaking the whole fault (T-instability) and combinations of both 4. Closed form equations that accurately describe the stability conditions for P-instabilities and T-instabilities 5. A useful framework to understand the full spectru...

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“…It was experimentally proven that small variations of the percentage of materials exhibiting properties of velocity strengthening and velocity weakening in the fault principal slip zone may result in significant variation of the share of seismic energy radiated during a fault slip event [3]. Tests simulated different modes of interblock sliding, scaled kinetic energy of those modes varied by several orders of magnitude, while differences in contact strength and shear stress drop remained relatively small.…”

Section: Institute Of Geosphere Dynamics Of Russian Academy Of Sciencmentioning

confidence: 99%

Different Fault Slip Modes - Governing, Evolution and Transformation

2019

International Workshop "Multiscale Biomechanics and Tribology of Inorganic and Organic Systems" ; Mezhdunarodnaja Konferencija

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A study of different fault slip modes governed by the gouge material composition in laboratory experiments

Cited by 31 publications

References 34 publications

Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

Stability of faults with heterogeneous friction properties and effective normal stress

Different Fault Slip Modes - Governing, Evolution and Transformation

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