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Jan Carmeliet - One of the best experts on this subject based on the ideXlab platform.
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Effect of grain fracture on stick-slip dynamics of granular Fault Gouge
2020Co-Authors: Di Wang, Omid Dorostkar, Chris Marone, Wei Zhou, Jan CarmelietAbstract:<p>Fault Gouge is produced by comminution, wear and other shearing processes that take place during geological tectonic movements. The frictional properties and stick-slip dynamics of granular Fault show similar patterns as geophysical phenomena like earthquakes and landslides. In this work, we introduce a particle breakage model in a granular Fault system to study the effect of grain fracture on the stick-slip dynamics. Our results show that particle breakage changes the macroscopic friction and the characteristics of slip events. By statistical analyses on a large number of slip events, we find that grain fracture changes the distribution of slip event size. During the evolution of crushable Fault Gouge, particle breakage does not lead to large slip events but triggers many small slips that partly dissipate the accumulated energy. On the other hand, the grain fracture is also influenced by the slip dynamics: it is shown that larger slip events will lead to a series of particle breakage due to localized high stresses during the rearrangement of granular Gouge. Our findings in this study show that in Faults with granular Gouge particle breakage significantly changes the characteristics of frictional instabilities and affects the dynamics of Fault system.</p>
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Potential Energy as Metric for Understanding Stick–Slip Dynamics in Sheared Granular Fault Gouge: A Coupled CFD–DEM Study
Rock Mechanics and Rock Engineering, 2018Co-Authors: Omid Dorostkar, Jan CarmelietAbstract:We study the stick–slip behavior in a sheared granular Fault Gouge using a coupled discrete element method and computational fluid dynamics. We compare characteristics of slip events in dry and fluid-saturated granular Fault Gouge in drained conditions. The granular layer is confined under constant normal load and sheared with a velocity-controlled mechanism. Potential energy is stored through overlaps between particles. We show that the potential energy builds up during the stick phase and drops during slip instability. Our observations show that on average 8% of the drop in potential energy is converted into particle kinetic energy, while the rest dissipates. Our simulations show that drop in potential energy is a good measure of slip size showing a strong correlation with the drop in macroscopic friction coefficient. Our simulations show that in fluid-saturated granular Fault Gouge, the potential energy drop is higher leading to a higher drop in friction coefficient and in a higher kinetic energy of particles during slip event.
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potential energy as metric for understanding stick slip dynamics in sheared granular Fault Gouge a coupled cfd dem study
Rock Mechanics and Rock Engineering, 2018Co-Authors: Omid Dorostkar, Jan CarmelietAbstract:We study the stick–slip behavior in a sheared granular Fault Gouge using a coupled discrete element method and computational fluid dynamics. We compare characteristics of slip events in dry and fluid-saturated granular Fault Gouge in drained conditions. The granular layer is confined under constant normal load and sheared with a velocity-controlled mechanism. Potential energy is stored through overlaps between particles. We show that the potential energy builds up during the stick phase and drops during slip instability. Our observations show that on average 8% of the drop in potential energy is converted into particle kinetic energy, while the rest dissipates. Our simulations show that drop in potential energy is a good measure of slip size showing a strong correlation with the drop in macroscopic friction coefficient. Our simulations show that in fluid-saturated granular Fault Gouge, the potential energy drop is higher leading to a higher drop in friction coefficient and in a higher kinetic energy of particles during slip event.
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cohesion induced stabilization in stick slip dynamics of weakly wet sheared granular Fault Gouge
Journal of Geophysical Research, 2018Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate Fault Gouge. The granular Gouge is constituted by 8000 spherical particles with a poly-disperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with two orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior, we show however, that at low confining stresses the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under which induced cohesion plays a significant role in Fault zone processes, including slip initiation, weakening, and failure.
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on the micromechanics of slip events in sheared fluid saturated Fault Gouge
Geophysical Research Letters, 2017Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We used a three-dimensional discrete element method coupled with computational fluid dynamics to study the poromechanical properties of dry and fluid saturated granular Fault Gouge. The granular layer was sheared under dry conditions to establish a steady state condition of stick-slip dynamic failure and then fluid was introduced to study its affect on subsequent failure events. The fluid saturated case showed increased stick-slip recurrence time and larger slip events compared to the dry case. Particle motion induces fluid flow with local pressure variation, which in turn leads to high particle kinetic energy during slip due to increased drag forces from fluid on particles. The presence of fluid during the stick phase of loading promotes a more stable configuration evidenced by higher particle coordination number. Our coupled fluid-particle simulations provide grain-scale information that improves understanding of slip instabilities and illuminates details of phenomenological, macro-scale observations.
Chris Marone - One of the best experts on this subject based on the ideXlab platform.
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Effect of grain fracture on stick-slip dynamics of granular Fault Gouge
2020Co-Authors: Di Wang, Omid Dorostkar, Chris Marone, Wei Zhou, Jan CarmelietAbstract:<p>Fault Gouge is produced by comminution, wear and other shearing processes that take place during geological tectonic movements. The frictional properties and stick-slip dynamics of granular Fault show similar patterns as geophysical phenomena like earthquakes and landslides. In this work, we introduce a particle breakage model in a granular Fault system to study the effect of grain fracture on the stick-slip dynamics. Our results show that particle breakage changes the macroscopic friction and the characteristics of slip events. By statistical analyses on a large number of slip events, we find that grain fracture changes the distribution of slip event size. During the evolution of crushable Fault Gouge, particle breakage does not lead to large slip events but triggers many small slips that partly dissipate the accumulated energy. On the other hand, the grain fracture is also influenced by the slip dynamics: it is shown that larger slip events will lead to a series of particle breakage due to localized high stresses during the rearrangement of granular Gouge. Our findings in this study show that in Faults with granular Gouge particle breakage significantly changes the characteristics of frictional instabilities and affects the dynamics of Fault system.</p>
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cohesion induced stabilization in stick slip dynamics of weakly wet sheared granular Fault Gouge
Journal of Geophysical Research, 2018Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate Fault Gouge. The granular Gouge is constituted by 8000 spherical particles with a poly-disperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with two orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior, we show however, that at low confining stresses the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under which induced cohesion plays a significant role in Fault zone processes, including slip initiation, weakening, and failure.
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on the micromechanics of slip events in sheared fluid saturated Fault Gouge
Geophysical Research Letters, 2017Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We used a three-dimensional discrete element method coupled with computational fluid dynamics to study the poromechanical properties of dry and fluid saturated granular Fault Gouge. The granular layer was sheared under dry conditions to establish a steady state condition of stick-slip dynamic failure and then fluid was introduced to study its affect on subsequent failure events. The fluid saturated case showed increased stick-slip recurrence time and larger slip events compared to the dry case. Particle motion induces fluid flow with local pressure variation, which in turn leads to high particle kinetic energy during slip due to increased drag forces from fluid on particles. The presence of fluid during the stick phase of loading promotes a more stable configuration evidenced by higher particle coordination number. Our coupled fluid-particle simulations provide grain-scale information that improves understanding of slip instabilities and illuminates details of phenomenological, macro-scale observations.
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On the role of fluids in stick-slip dynamics of saturated granular Fault Gouge using a coupled computational fluid dynamics-discrete element approach
Journal of Geophysical Research: Solid Earth, 2017Co-Authors: Omid Dorostkar, Chris Marone, Robert A. Guyer, Paul A. Johnson, Jan CarmelietAbstract:The presence of Fault Gouge has considerable influence on slip properties of tectonic Faults and the physics of earthquake rupture. The presence of fluids within Faults also plays a significant role in Faulting and earthquake processes. In this paper, we present 3-D discrete element simulations of dry and fluid-saturated granular Fault Gouge and analyze the effect of fluids on stick-slip behavior. Fluid flow is modeled using computational fluid dynamics based on the Navier-Stokes equations for an incompressible fluid and modified to take into account the presence of particles. Analysis of a long time train of slip events shows that the (1) drop in shear stress, (2) compaction of granular layer, and (3) the kinetic energy release during slip all increase in magnitude in the presence of an incompressible fluid, compared to dry conditions. We also observe that on average, the recurrence interval between slip events is longer for fluid-saturated granular Fault Gouge compared to the dry case. This observation is consistent with the occurrence of larger events in the presence of fluid. It is found that the increase in kinetic energy during slip events for saturated conditions can be attributed to the increased fluid flow during slip. Our observations emphasize the important role that fluid flow and fluid-particle interactions play in tectonic Fault zones and show in particular how discrete element method (DEM) models can help understand the hydromechanical processes that dictate Fault slip.
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Laboratory observation of acoustic fluidization in granular Fault Gouge and implications for dynamic weakening of earthquake Faults
Geochemistry Geophysics Geosystems, 2013Co-Authors: Kaiwen Xia, Sheng Huang, Chris MaroneAbstract:[1] Several lines of evidence, including remote triggering of earthquakes and modulation of seismic tremor by Earth tides, suggest that Faults weaken when subject to shaking and dynamic stresses associated with the passage of seismic waves. However, the origin of such dynamic weakening is poorly understood. Here we explore the role of acoustic resonance for dynamic Fault weakening using laboratory measurements. Experiments were conducted using a split Hopkinson pressure bar assembly, with dynamic stressing via impact loading. Samples were composed of crushed rock particles from mine tailings with a particle size distribution similar to that found in a natural Fault Gouge. We used pulse-shaper techniques and carefully evaluated dynamic stresses recorded at the front and rear of the sample to ensure that dynamic force balance was satisfied. Our experiments document acoustic-induced fluidization and dramatic dynamic weakening. Frictional strength and elastic modulus of a simulated Fault Gouge are reduced by a factor of 5–10 via acoustic fluidization. We find a threshold acoustic pressure for fluidization that varies systematically with Gouge zone properties. Our observations could help explain dynamic Fault weakening and triggering of earthquake Fault slip by dynamic stressing.
Omid Dorostkar - One of the best experts on this subject based on the ideXlab platform.
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Effect of grain fracture on stick-slip dynamics of granular Fault Gouge
2020Co-Authors: Di Wang, Omid Dorostkar, Chris Marone, Wei Zhou, Jan CarmelietAbstract:<p>Fault Gouge is produced by comminution, wear and other shearing processes that take place during geological tectonic movements. The frictional properties and stick-slip dynamics of granular Fault show similar patterns as geophysical phenomena like earthquakes and landslides. In this work, we introduce a particle breakage model in a granular Fault system to study the effect of grain fracture on the stick-slip dynamics. Our results show that particle breakage changes the macroscopic friction and the characteristics of slip events. By statistical analyses on a large number of slip events, we find that grain fracture changes the distribution of slip event size. During the evolution of crushable Fault Gouge, particle breakage does not lead to large slip events but triggers many small slips that partly dissipate the accumulated energy. On the other hand, the grain fracture is also influenced by the slip dynamics: it is shown that larger slip events will lead to a series of particle breakage due to localized high stresses during the rearrangement of granular Gouge. Our findings in this study show that in Faults with granular Gouge particle breakage significantly changes the characteristics of frictional instabilities and affects the dynamics of Fault system.</p>
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Potential Energy as Metric for Understanding Stick–Slip Dynamics in Sheared Granular Fault Gouge: A Coupled CFD–DEM Study
Rock Mechanics and Rock Engineering, 2018Co-Authors: Omid Dorostkar, Jan CarmelietAbstract:We study the stick–slip behavior in a sheared granular Fault Gouge using a coupled discrete element method and computational fluid dynamics. We compare characteristics of slip events in dry and fluid-saturated granular Fault Gouge in drained conditions. The granular layer is confined under constant normal load and sheared with a velocity-controlled mechanism. Potential energy is stored through overlaps between particles. We show that the potential energy builds up during the stick phase and drops during slip instability. Our observations show that on average 8% of the drop in potential energy is converted into particle kinetic energy, while the rest dissipates. Our simulations show that drop in potential energy is a good measure of slip size showing a strong correlation with the drop in macroscopic friction coefficient. Our simulations show that in fluid-saturated granular Fault Gouge, the potential energy drop is higher leading to a higher drop in friction coefficient and in a higher kinetic energy of particles during slip event.
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potential energy as metric for understanding stick slip dynamics in sheared granular Fault Gouge a coupled cfd dem study
Rock Mechanics and Rock Engineering, 2018Co-Authors: Omid Dorostkar, Jan CarmelietAbstract:We study the stick–slip behavior in a sheared granular Fault Gouge using a coupled discrete element method and computational fluid dynamics. We compare characteristics of slip events in dry and fluid-saturated granular Fault Gouge in drained conditions. The granular layer is confined under constant normal load and sheared with a velocity-controlled mechanism. Potential energy is stored through overlaps between particles. We show that the potential energy builds up during the stick phase and drops during slip instability. Our observations show that on average 8% of the drop in potential energy is converted into particle kinetic energy, while the rest dissipates. Our simulations show that drop in potential energy is a good measure of slip size showing a strong correlation with the drop in macroscopic friction coefficient. Our simulations show that in fluid-saturated granular Fault Gouge, the potential energy drop is higher leading to a higher drop in friction coefficient and in a higher kinetic energy of particles during slip event.
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cohesion induced stabilization in stick slip dynamics of weakly wet sheared granular Fault Gouge
Journal of Geophysical Research, 2018Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate Fault Gouge. The granular Gouge is constituted by 8000 spherical particles with a poly-disperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with two orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior, we show however, that at low confining stresses the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under which induced cohesion plays a significant role in Fault zone processes, including slip initiation, weakening, and failure.
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on the micromechanics of slip events in sheared fluid saturated Fault Gouge
Geophysical Research Letters, 2017Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We used a three-dimensional discrete element method coupled with computational fluid dynamics to study the poromechanical properties of dry and fluid saturated granular Fault Gouge. The granular layer was sheared under dry conditions to establish a steady state condition of stick-slip dynamic failure and then fluid was introduced to study its affect on subsequent failure events. The fluid saturated case showed increased stick-slip recurrence time and larger slip events compared to the dry case. Particle motion induces fluid flow with local pressure variation, which in turn leads to high particle kinetic energy during slip due to increased drag forces from fluid on particles. The presence of fluid during the stick phase of loading promotes a more stable configuration evidenced by higher particle coordination number. Our coupled fluid-particle simulations provide grain-scale information that improves understanding of slip instabilities and illuminates details of phenomenological, macro-scale observations.
R A Guyer - One of the best experts on this subject based on the ideXlab platform.
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cohesion induced stabilization in stick slip dynamics of weakly wet sheared granular Fault Gouge
Journal of Geophysical Research, 2018Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate Fault Gouge. The granular Gouge is constituted by 8000 spherical particles with a poly-disperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with two orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior, we show however, that at low confining stresses the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under which induced cohesion plays a significant role in Fault zone processes, including slip initiation, weakening, and failure.
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on the micromechanics of slip events in sheared fluid saturated Fault Gouge
Geophysical Research Letters, 2017Co-Authors: Omid Dorostkar, Jan Carmeliet, Chris Marone, Paul A. Johnson, R A GuyerAbstract:We used a three-dimensional discrete element method coupled with computational fluid dynamics to study the poromechanical properties of dry and fluid saturated granular Fault Gouge. The granular layer was sheared under dry conditions to establish a steady state condition of stick-slip dynamic failure and then fluid was introduced to study its affect on subsequent failure events. The fluid saturated case showed increased stick-slip recurrence time and larger slip events compared to the dry case. Particle motion induces fluid flow with local pressure variation, which in turn leads to high particle kinetic energy during slip due to increased drag forces from fluid on particles. The presence of fluid during the stick phase of loading promotes a more stable configuration evidenced by higher particle coordination number. Our coupled fluid-particle simulations provide grain-scale information that improves understanding of slip instabilities and illuminates details of phenomenological, macro-scale observations.
Toshihiko Shimamoto - One of the best experts on this subject based on the ideXlab platform.
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high velocity frictional behavior and microstructure evolution of Fault Gouge obtained from nojima Fault southwest japan
Tectonophysics, 2009Co-Authors: Kazuo Mizoguchi, Toshihiko Shimamoto, Takehiro Hirose, Eiichi FukuyamaAbstract:Abstract High-velocity experiments on Fault Gouge taken from the Nojima Fault that slipped during the 1995 Kobe earthquake were conducted to investigate physical mechanism associated with the slip-weakening behavior. With increasing slip, the friction values of the Gouge sheared at 0.62 MPa normal stress and 1.03 m/s slip velocity decrease exponentially from a peak value of more than 0.6 to a steady-state value of 0.2. The textures of the Gouge are characterized by grain comminution, oblique and parallel shear planes and localized deformation zone with strongly preferred orientation in the friction weakening stage, and folding and fluttering structures at the steady-state friction stage. Numerical modeling based on the temperature measurements close to the Gouge layer shows that the temperature inside the gauge layer did not exceed 400 °C during the experiments. In a slide–hold–slide test, a full strength recovery of the Fault Gouge was observed only after 12 s slip pause and the slip-weakening curves are the same between the two successive slips. The steady-state coefficient of friction decreased from 0.8 to about 0.2 when the slip velocity increased from 0.006 m/s to 1.03 m/s. This high-velocity weakening feature was observed in a synthetic quartz Gouge as well as in the Nojima Gouge. Although it is unclear which mechanism causes the weakening among thermal pressurization, silica gel lubrication, flash heating, moisture-draining and so on, the present experimental results suggest that the high-velocity weakening is related to the high heat production rate. Finally, the flow structures observed in the samples deformed up to the final steady-state stages have never been reported in previous slow-rate experiments and could be a key structure characteristic of high-velocity frictional sliding.
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Constitutive properties of clayey Fault Gouge from the Hanaore Fault zone, southwest Japan
Journal of Geophysical Research, 2009Co-Authors: Hiroyuki Noda, Toshihiko ShimamotoAbstract:Velocity step tests at a range of slip rates (0.0154–155.54 μm s^(−1)) are performed using natural Fault Gouge containing smectite, mica, and quartz collected from an outcrop of the Hanaore Fault, southwest Japan. Field and microscopic observations reveal that the shear deformation is localized to a few centimeters or thinner layer of black clayey Fault Gouge. This layer is formed by multiple stages, and determining the width of the shear zone due to a single event is difficult to determine. The experimental data on the abrupt jumps in the load point velocity are fitted by a rate‐ and state‐dependent frictional law, coupled with the spring‐slider model, the stiffness of which is treated as a fitting parameter. This treatment is shown to be essential to determine the constitutive parameters and their errors. The velocity steps are successfully fit with typically two state variables: larger b_1 with shorter d_(c1) and smaller b_2 with longer d_(c2). At slip rates higher than 1 μm s^(−1), negative b_2 is required to fit the data in most of the cases. Thin Gouge layers (∼200 μm) in the experiment enables us to simulate large averaged shear strain which is important to recognize the evolution of the state variable associated with negative b_2 and long d_(c2). Observation of microscopic structure after experiments shows poor development of Y planes. This may be consistent with the mechanical behavior observed: weak occurrence of initial peak strength at yielding and displacement hardening throughout the experiments.
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gas permeability evolution of cataclasite and Fault Gouge in triaxial compression and implications for changes in Fault zone permeability structure through the earthquake cycle
Tectonophysics, 2004Co-Authors: Shin Ichi Uehara, Toshihiko ShimamotoAbstract:Abstract We report the results of permeability measurements of Fault Gouge and tonalitic cataclasite from the Fault zone of the Median Tectonic Line, Ohshika, central Japan, carried out during triaxial compression tests. The experiments revealed marked effects of deformation on the permeability of the specimens. Permeability of Fault Gouge decreases rapidly by about two orders of magnitude during initial loading and continues to decrease slowly during further inelastic deformation. The drop in permeability during initial loading is much smaller for cataclasite than for Gouge, followed by abrupt increase upon failure, and the overall change in permeability correlates well with change in volumetric strain, i.e., initial, nearly elastic contraction followed by dilatancy upon the initiation of inelastic deformation towards specimen failure. If cemented cataclasite suffers deformation prior to or during an earthquake, a cataclasite zone may change into a conduit for fluid flow. Fault Gouge zones, however, are unlikely to switch to very permeable zones upon the initiation of Fault slip. Thus, overall permeability structure of a Fault may change abruptly prior to or during earthquakes and during the interseismic period. Fault Gouge and cataclasite have internal angles of friction of about 36° and 45°, respectively, as is typical for brittle rocks.
