Characterization of Carbopol® hydrogel rheology for experimental tectonics and geodynamics

Giuseppe, Erika Di; Corbi, Fabio; Funiciello, Francesca; Maßmeyer, A.; Santimano, Tasca; Rosenau, Matthias; Davaille, Anne

doi:10.1016/j.tecto.2014.12.005

Cited by 82 publications

(54 citation statements)

References 90 publications

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“…As with gelatine, Carbopol ® rheology depends on its concentration but also additionally on pH. It is very shear thinning and has a yield strength of up to a few hundred pascal (Di Giuseppe et al, 2015). It is consequently rheologically modelled as a Herschel-Buckley fluid.…”

Section: Viscoelastic Rock Analogue Materialsmentioning

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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Section: Viscoelastic Rock Analogue Materialsmentioning

confidence: 99%

Analogue earthquakes and seismic cycles: experimental modelling across timescales

2017

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“…The viscosity of all the experiments is close to 10 3 Pa s, except for that with the smallest concentration, for which the viscosity is lower (∼10 2 Pa s). We prepare the gel according to an established preparation recipe 33 and use a newly prepared batch of Carbopol for each experiment. After hydration and neutralization we stir the gel for 2 h and let it equilibrate for 48 h. Viscosity and yield stress were measured with an AR 2000ex rheometer that imposes a torsional flow on the sample (parallel plates, gap width: 1 mm, shear rate range: 0.01-100 s −1 ).…”

Section: Materialmentioning

confidence: 99%

“…Data points of sweep experiments can be fitted with a Herschel-Bulkley rheology 16,33 , suggesting that Carbopol is a power-law yield stress fluid that exhibits an elastic behaviour up to a shear strain of 2% (ref. 34).…”

Section: Materialmentioning

confidence: 99%

Experimental demonstration of a semi-brittle origin for crustal strain transients

2015

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Tectonic motions give rise to destructive earthquakes and transient slip events. These movements are often described by friction laws for stick-slip motion on brittle fault surfaces and gouge-filled zones 1,2 . Yet, many transient slip events, such as slow earthquakes and aseismic creep, occur in rocks that exhibit mixed brittle-ductile rheology, where these friction laws are not clearly applicable 3,4 . Here we describe the flow and evolution of fractures as observed in a semi-brittle rock analogue exposed to shear stress in laboratory experiments. We find that, depending on the strength of the rock-analogue material, and thus the magnitude of yield stress, the material exhibits either creep-like or stick-slip behaviour. At low yield stress, deformation occurs as constant creep along a main fracture, whereas at high yield stress, the material exhibits stick-slip behaviour. However, the deformation does not involve frictional behaviour; it is instead accommodated by the initiation and growth of a system of tensional and shear fractures. The opening and interplay of such fracture systems could generate tectonic tremor and slow slip. Our laboratory experiments thus support a frictionless alternative mechanism for the development of tectonic strain transients.Semi-brittle deformation in geologic systems is generally defined micromechanically 5-7 , wherein fracturing and/or frictional sliding characterizes the deformation of one mineral phase while another flows through viscous deformation mechanisms. In the resulting meso-scale deformation, rather than accommodate strain via a single, brittle shear fracture or continuous, ductile creep, there is a combination of both brittle and ductile deformation. Field observations of semi-brittle rocks show that for a range of composition, temperature and pressure, the formation of fluid-filled brittle fractures and veins accompanies localized ductile flow 3,4,8 . At the scale of the lithosphere, the transition from brittle to ductile deformation is highly temperature-sensitive, and thus such semibrittle deformation is particularly important at a depth interval in the lithosphere near the base of the seismogenic zone referred to as the brittle-to-ductile transition (BDT; refs 6,7). A wide variety of slip behaviours have been geophysically resolved to originate in the BDT, and observations and physical experiments of semibrittle materials show that the coexistence of brittle and viscous behaviour gives emergence to some of the characteristics of strain transients and slow slip events 9-11 . However, most workers explain differences in slip transients with laws that describe how fluid pressure, temperature changes and friction interact 12 . Here, we explore an alternative mechanism where strain transients ranging from stick-slip to creep can be explained by the co-occurrence of brittle and ductile deformation.Semi-brittle deformation has been studied in a variety of rock mechanics experiments 5,13 . Although constraining flow laws under laboratory conditions, these experiments are...

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“…Carbopol has overall lower viscosities, but has been described to exhibit a yield stress (i.e., a stress below which no flow occurs) instead of a low-stress Newtonian plateau (Di Giuseppe et al, 2015), and viscosity decreases excessively at the stress range of interest. Natrosol solutions such as described by nicely show a constant viscosity for low stresses, a slightly too low stress exponent (n ≈ 2), while the viscosities are less than needed for lithospheric application.…”

Section: Previous Studies On Power-law Analogue Materialsmentioning

confidence: 99%

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

Broerse¹,

Norder²,

Govers³

et al. 2018

Preprint

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Stress-dependent nonlinear upper mantle rheology has a firm base in rock mechanical tests, where this nonlinearity results from dislocation creep of minerals. In the last few decades there has been some attention to nonlinear, power-law, materials for application in scaled analogue experiments for tectonic processes. However, studies describing the rheology of analogue materials with the same nonlinear dependency on stress as observed for lithospheric mantle materials at relevant stress levels, are still lacking.In this study we have developed and rheologically tested materials based on combinations of silicone polymers and plasticine, with the aim of obtaining a material that can serve as a laboratory analogue to the power-law rheology of olivine aggregates at lithospheric mantle conditions. From our steadystate creep tests we find that it is possible to obtain such a power-law material, with effective viscosities over relevant model stress ranges We apply the developed material to a process where localized deformation of the lithosphere can be expected: slab break-off. We study this process using analogue models, where we apply the new nonlinear material to the lithospheric mantle domains, while we use Newtonian glucose to represent the low viscous asthenosphere. Now that we properly manage power-law behavior in our analogue lithosphere materials, we are able to model localized lithospheric tearing.

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Characterization of Carbopol® hydrogel rheology for experimental tectonics and geodynamics

Cited by 82 publications

References 90 publications

Analogue earthquakes and seismic cycles: experimental modelling across timescales

Analogue earthquakes and seismic cycles: experimental modelling across timescales

Experimental demonstration of a semi-brittle origin for crustal strain transients

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

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