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This data set provides a series of experiments from ring-shear tests (RST) on various materials that are used at several laboratories worldwide. The data contains the results of slide-hold-slide tests and the processed outputs of standardized ring shear tester data from related publications. Additionally, microscopy images of the materials under plain and polarized light are provided. The time dependent restrengthening of the materials is quantified using slide-hold-slide tests. This restrengthening has implications on the reactivation potential of granular shear zones in analogue models. With the provided software we first analyze the experimental data and then compare the angles and stresses needed to reactivate normal faults in the materials. We find that while healing rates are low, the majority of samples can not reactivate normal faults that are generated through extension of an analogue model.
This dataset provides friction data from ring-shear tests on glass beads with a diameter of 200-300 µm used in analogue modelling of tectonic processes as a rock analogue for “weak” layers in the earth’s upper crust (e.g. Klinkmüller et al., 2016; Ritter et al., 2016; Lohrmann et al., 2003) or as “seismogenic” crust (Rudolf et al., 2022). The glass beads are characterized by means of internal friction coefficients µ and cohesion C. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak, dynamic and reactivation friction coefficients of the glass beads are µP = 0.51 , µD = 0.40, and µR = 0.44, respectively (Table 5). Cohesion of the material ranges between 40 Pa and 70 Pa. The material shows a minor rate-weakening of ~1% per ten-fold change in shear velocity v and a stick-slip behaviour at low shear velocities and at high loads.
This dataset provides friction data from ring-shear tests on glass beads with a diameter of 100-200 µm used in analogue modelling of tectonic processes as a rock analogue for “weak” layers in the earth’s upper crust (e.g. Klinkmüller et al., 2016; Ritter et al., 2016; Lohrmann et al., 2003) or as “seismogenic” crust (Rudolf et al., 2022). The glass beads are characterized by means of internal friction coefficients µ and cohesion C. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak, dynamic and reactivation friction coefficients of the glass beads are µP = 0.50 , µD = 0.39, and µR = 0.46, respectively (Table 5). Cohesion of the material is close to zero Pa. The material shows a minor rate-weakening of ~1% per ten-fold change in shear velocity v and a stick-slip behaviour at low shear velocities and at high loads.
This dataset provides friction data from ring-shear tests on glass beads with a diameter of less than 50 µm used in analogue modelling of tectonic processes as a rock analogue for “weak” layers in the earth’s upper crust (e.g. Klinkmüller et al., 2016; Ritter et al., 2016; Lohrmann et al., 2003) or as “seismogenic” crust (Rudolf et al., 2022). The glass beads are characterized by means of internal friction coefficients µ and cohesion C. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak, dynamic and reactivation friction coefficients of the glass beads are µP = 0.47 , µD = 0.44, and µR = 0.47, respectively (Table 5). Cohesion of the material ranges between 50 Pa and 70 Pa. The material shows a neglectable rate-weakening of <1% per ten-fold change in shear velocity v.
This data set provides two series of experiments from ring-shear tests (RST) on glass beads that are in use at the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam. The main experimental series contains shear experiments to analyse the slip behaviour of the granular material under analogue experiment conditions. Additionally, a series of slide-hold-slide (SHS) tests was used to determine the rate and state friction properties. A basic characterisation and average friction coefficients of the glass beads are found in Pohlenz et al. (2020). The glass beads show a slip behaviour that is depending on loading rate, normal stress and apparatus stiffness which were varied systematically for this study. The apparatus was modified with springs resulting in 4 different stiffnesses. For each stiffness a set of 4 experiments with different normal stresses (5, 10, 15 and 20 kPa) were performed. During each experiment loading rate was decreased from 0.02 to 0.0008 mm/s resulting in 9 subsets of constant velocity for each experiment. We observe a large variety of slip modes that ranges from pure stick-slip to steady state creep. The main characteristics of these slip modes are the slip velocity and the ratio of slip event duration compared to no slip phases. We find that high loading rates promote stable slip, while low loading rates lead to stick-slip cycles. Lowering the normal stress leads to a larger amount of creep which changes the overall shape of a stick-slip curve and extends the time between slip events. Changing stiffness leads to an overall change in slip behaviour switching from simple stick-slip to more complex patterns of slip modes including oscillations and bimodal slip events with large and small events. The SHS tests were done at maximum stiffness and higher loading rates (>0.05 mm/s) but at the same normal stress intervals as the main series. Using various techniques, we estimate the rate-and-state constitutive parameters. The peak stress after a certain amount of holding increases with a healing rate of b=0.0057±0.0005. From the increase in peak stress compared to the loading rate in slide-hold-slide tests we compute a direct effect a=-0.0076±0.0005 which leads to (a-b)=-0.0130±0.0006. Using a specific subset of the SHS tests, which have an equal ratio of hold time to reloading rate, we estimate (a-b)=-0.0087±0.0029. Both approaches show that the material is velocity weakening with a reduction in friction of 1.30 to 0.87 % per e-fold increase in loading rate. Additionally, the critical slip distance Dc is estimated to be in the range of 200 µm. With these parameters the theoretical critical stiffness kc is estimated and applied to the slip modes found in the main series. We find that the changes in slip mode are in good agreement with the estimated critical stiffness and thus confirm the findings from the SHS tests.
The southern Andes are regarded as a typical subduction orogen formed by oblique plate convergence. Despite decades of studies, there is considerable uncertainty as to how deformation is kinematically partitioned in the upper plate. Using scaled analogue experiments modelling, we test the concept of dextral transpression for this orogen. We advocate that the GPS velocity field portrays interseismic deformation related to deformation of strong crust north, and weak crust south, of 37°S. Contrary to the popular hypotheses that the Liquiñe-Ofqui Fault Zone, a prominent intra-arc deformation zone, takes up most of the plate boundary-parallel dextral strike-slip, we find that dextral transpression affects the entire model orogen through tectonic segmentation of crust. Moreover, prominent, regularly spaced sinistral oblique-slip thrust faults, interpreted as antithetic Riedel shears, developed spontaneously in all of our experiments and call into question the general believe that their NW-striking natural equivalents formed from pre-Andean discontinuities. Our experiments prompt us to reconsider the apparently well-established geodynamic concept that strain and margin-parallel displacement is localized on a few margin-parallel faults in the southern Andes.
The dataset presented here contains the results of mechanical testing of two granular materials (quartz sand and glass micro beads) that are commonly used in analogue tectonic experiments. The data were acquired using a ring-shear tester RST-01.pc [Schulze, 1994]. Tests were performed at different normal loads ranging from 125 Pa to 4000 Pa and with eight to ten repetitions per normal load and material. The parameters measured are: rotation velocity, shear stress, normal load and sample dilation, all as a function of time. A detailed analysis and interpretation of the data can be found in the main article of [Ritter et al., 2016]. The data were measured in the ring-shear tester RST-01.pc [Schulze, 1994, see below] at GFZ Potsdam’s analogue laboratory for tectonic modelling. All samples have been prepared and measured by the same person. Preparation was by sifting from a constant height of 30 cm into the shear cell. Tests were performed at different normal loads ranging from 125 Pa to 4000 Pa and with eight to ten repetitions per normal load and material. For normal loads below 500 Pa, the samples were pre-loaded by shortly increasing the normal load to 500 Pa and then resetting it to the desired value prior to the onset of deformation. This pre-loading was carried out for technical reasons. Preliminary tests at a normal load of 300 Pa have shown that this does not affect the strength. The data are presented as shear curves in tab-separated text files. The file names consist of (in this order) material, normal load and a running number. Each file contains one shear curve and consists of a header describing the individual measurements followed by a table with one column per parameter (read more in the dataset description pdf). References: Schulze, D. (1994) Entwicklung und Anwendung eines neuartigen Ringschergerätes, Aufbereitungstechnik, 35(10), 524–535.
This dataset provides sieve data (grain size distributions) on natural and artificial granular materials used for experimental simulation by the analogue geodynamic modelling community (21 sands and glass beads). The material samples have been collected community-wide and analysed at GFZ Potsdam in the framework of the GeoMod2008 conference benchmark initiative. The context of data collection, details of the material samples and measuring techniques as well as interpretation and discussion of results can be found in Klinkmüller et al. (2016) to which this dataset is supplement material.
This dataset provides friction data from ring shear test (RST) on natural and artificial granular materials used for experimental simulation by the analogue geodynamic modelling community (21 sands and glass beads). The material samples have been collected community-wide and analysed at GFZ Potsdam in the framework of the GeoMod2008 conference benchmark initiative. The context of data collection, details of the material samples and measuring techniques as well as interpretation and discussion of results can be found in Klinkmüller et al. (2016) to which this dataset is supplement material.
This dataset provides compaction data from axial testing on natural and artificial granular materials used for experimental simulation by the analogue geodynamic modelling community (21 sands and glass beads). The material samples have been collected community-wide and analysed at GFZ Potsdam in the framework of the GeoMod2008 conference benchmark initiative. The context of data collection, details of the material samples and measuring techniques as well as interpretation and discussion of results can be found in Klinkmüller et al. (2016) to which this dataset is supplement material.
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