Microslips as precursors of large slip events in the stick‐slip dynamics of sheared granular layers: A discrete element model analysis

Ferdowsi, Behrooz; Griffa, Michele; Guyer, R. A.; Johnson, P. A.; Marone, Chris; Carmeliet, Jan

doi:10.1002/grl.50813

Cited by 56 publications

(73 citation statements)

References 38 publications

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“…The sample size in our simulations is 11 × 1.5 × 0.8 mm that is equivalent to 6.7 d p in depth (direction y in Figure ), 12.5 d p in height (direction z in Figure ), and 91.7 d p in length (direction x in Figure ), respectively, where d p is mean particle diameter, 120 μm. We remark that as a guideline, previous numerical simulations have shown that the nature of stick‐slip dynamics and distribution of slip event size remains almost unchanged for different sample sizes if appropriate size (equal to or bigger than 4 d p ) is produced in depth of such granular fault gouge [ Ferdowsi et al ., ; Ferdowsi , ].…”

Section: Numerical Setupmentioning

confidence: 99%

“…The nature of stress accommodation and the dynamics of the stick‐slip events have been well studied in laboratory experiments and numerical simulations primarily on dry granular fault gouge [ Marone , , ; Morgan , ; Mair et al ., ; Guo and Morgan , ; Anthony and Marone , ; Johnson and Jia , ; Mair and Hazzard , ; Johnson et al ., ; Samuelson et al ., ; Johnson et al ., ; Johnson et al ., ]. Recent 3‐D discrete element method (DEM) numerical simulations of dry granular fault gouge demonstrate both spontaneous and triggered stick‐slip [ Ferdowsi et al ., ; Griffa et al ., ; Ferdowsi et al ., , ] similar to experiments. There exist a few studies of fluid‐saturated granular fault gouge as well.…”

Section: Introductionmentioning

confidence: 99%

“…[] studied the mechanical coupling of fluid‐filled granular materials under shear with a 2‐D DEM model. Both experimental and field‐scale studies [ Sutherland et al ., ] have shown the significance of 3‐D aspects, such as particle rearrangements [ Ferdowsi et al ., ] and 3‐D fluid flow within a granular fault gouge [ Achtziger‐Zupančič et al ., ]. The size and timing of consecutive slip events are the two main characteristics of a stick‐slip sequence.…”

Section: Introductionmentioning

confidence: 99%

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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

et al. 2017

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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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Section: Numerical Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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

et al. 2017

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“…These experiments were accompanied by numerical models mainly using the discrete element method (e.g. Abe and Mair, 2009;Abe et al, 2006;Ferdowsi et al, 2013Ferdowsi et al, , 2014Ferdowsi et al, , 2015Mair and Abe, 2008;Mair and Hazzard, 2007). The shearing of optically clear acrylic or polymeric spheres and discs (e.g.…”

Section: Spring-slider Modelsmentioning

confidence: 99%

Analogue earthquakes and seismic cycles: experimental modelling across timescales

2017

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Abstract. Earth deformation is a multi-scale process ranging from seconds (seismic deformation) to millions of years (tectonic deformation). Bridging short-and long-term deformation and developing seismotectonic models has been a challenge in experimental tectonics for more than a century. Since the formulation of Reid's elastic rebound theory 100 years ago, laboratory mechanical models combining frictional and elastic elements have been used to study the dynamics of earthquakes. In the last decade, with the advent of high-resolution monitoring techniques and new rock analogue materials, laboratory earthquake experiments have evolved from simple spring-slider models to scaled analogue models. This evolution was accomplished by advances in seismology and geodesy along with relatively frequent occurrences of large earthquakes in the past decade. This coincidence has significantly increased the quality and quantity of relevant observations in nature and triggered a new understanding of earthquake dynamics. We review here the developments in analogue earthquake modelling with a focus on those seismotectonic scale models that are directly comparable to observational data on short to long timescales. We lay out the basics of analogue modelling, namely scaling, materials and monitoring, as applied in seismotectonic modelling. An overview of applications highlights the contributions of analogue earthquake models in bridging timescales of observations including earthquake statistics, rupture dynamics, ground motion, and seismic-cycle deformation up to seismotectonic evolution.

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“…Indeed, the resistance to shear stress of seismic faults is typically much larger than the one obtained in experiments measuring the friction coefficient of sliding rocks [15]. Furthermore, remote triggering of earthquakes [16][17][18][19][20] at distances of thousand kilometers from the main shock epicenter indicates a high susceptibility of seismic faults to the passage of seismic waves. The hypothesis of Acoustic Fluidization (AF), formulated by Melosh [21,22], provides an answer to both questions.…”

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confidence: 99%

Synchronized oscillations and acoustic fluidization in confined granular materials

et al. 2018

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According to the acoustic fluidization hypothesis, elastic waves at a characteristic frequency form inside seismic faults even in absence of an external perturbation. These waves are able to generate a normal stress which contrasts the confining pressure and promotes failure. Here we study the mechanisms responsible for this wave activation via numerical simulations of a granular fault model. We observe the particles belonging to the percolating backbone, which sustains the stress, to perform synchronized oscillations over elliptic-like trajectories in the fault plane. These oscillations occur at the characteristic frequency of acoustic fluidization. As the applied shear stress increases, these oscillations become perpendicular to the fault plane just before the system fail, opposing to the confining pressure, consistently with the acoustic fluidization scenario. The same change of orientation can be induced by external perturbations at the acoustic fluidization frequency.PACS numbers: 45.70.Vn, 63.50.Lm, 91.30.Px Confined granular materials under shear display the typical stick-slip dynamics observed in real fault systems. In the last years this dynamics has been deeply investigated in several experimental settings as well as by means of molecular dynamics simulations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These studies mostly focus on two central questions: i) Why the stress responsible for seismic failure is usually orders of magnitude smaller than the value expected on the basis of rock fracture mechanics? ii) Why seismic faults are very susceptible to even small amplitude transient seismic waves? Indeed, the resistance to shear stress of seismic faults is typically much larger than the one obtained in experiments measuring the friction coefficient of sliding rocks [15]. Furthermore, remote triggering of earthquakes [16][17][18][19][20] at distances of thousand kilometers from the main shock epicenter indicates a high susceptibility of seismic faults to the passage of seismic waves. The hypothesis of Acoustic Fluidization (AF), formulated by Melosh [21,22], provides an answer to both questions. According to AF, the elastic waves produced by seismic fracture, at a characteristic frequency ω AF , diffuse and scatter inside the fault and then generate a normal stress which can contrast the confining pressure. In this way seismic failure is promoted. To investigate this scenario, experimental studies [1,2,6,7] have demonstrated that acoustic perturbations modify granular rheology and lead to auto-acoustic compaction [7]. Recently the AF scenario has been explored in 3D molecular dynamics simulations [23] which have shown that weak external perturbations, at the frequency ω AF , even if increasing the confining pressure or reducing the applied shear, induce slip instabilities. Interestingly simulations have also shown that oscillations at the frequency ω AF are activated immediately before each slip, even in the absence of an external perturbation. Nevertheless the mechanisms responsible for this ac...

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Microslips as precursors of large slip events in the stick‐slip dynamics of sheared granular layers: A discrete element model analysis

Cited by 56 publications

References 38 publications

On the role of fluids in stick‐slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics‐discrete element approach

On the role of fluids in stick‐slip dynamics of saturated granular fault gouge using a coupled computational fluid dynamics‐discrete element approach

Analogue earthquakes and seismic cycles: experimental modelling across timescales

Synchronized oscillations and acoustic fluidization in confined granular materials

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