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Cyclic loading stress-strain data in polycrystalline antigorite serpentinite, at various confining pressures and temperatures. This dataset is used and fully described/interpreted in the paper: David, E.C., N. Brantut, and G. Hirth, Sliding crack model for non-linearity and hysteresis in the triaxial stress-strain curve of rock, and application to antigorite deformation, submitted to J. Geophys. Res. Overview Rock type Vermont antigorite-rich (>95%) serpentinite. See submitted paper for details. The sample is isotropic. Apparatus Oil-medium triaxial apparatus (Rock Physics Ensemble, University College London). For description, see David el al. (2018), Absence of stress-induced anisotropy during brittle deformation in antigorite serpentinite, J. Geophys. Res., 123, 10616-10644. Griggs-type solid medium apparatus (Brown University). For description, see David, E.C., N. Brantut, and G. Hirth, Sliding crack model for non-linearity and hysteresis in the triaxial stress-strain curve of rock, and application to antigorite deformation, submitted to J. Geophys. Res., and references therein. Files description 1-existing data from David et al., JGR, 2018: The text file "Vermont-antigorite-roomT-150MPa-stress-strain-cyclicloading-UCLtriax" gives the axial stress (in direction 1, see submitted paper) and the axial strain (in percent, in direction 1, see submitted paper), at room temperature and 150 MPa confining pressure, in the oil triaxial apparatus at UCL. The mechanical data (stress, strain) have been corrected from internal friction and machine stiffness, respectively. The data are from David el al. (2018), Absence of stress-induced anisotropy during brittle deformation in antigorite serpentinite, J. Geophys. Res., 123, 10616-10644. 2-new data: The text file "Vermont-antigorite-roomT-1000MPa-stress-strain-cyclicloading-Griggsapparatus" gives the axial stress (in direction 1, see submitted paper) and the axial strain (in percent, in direction 1, see submitted paper), at room temperature and 1000 MPa confining pressure, in Griggs solid medium apparatus at Brown University. The mechanical data (stress, strain) have been corrected from internal friction and machine stiffness, respectively. The text file "Vermont-antigorite-400C-1000MPa-stress-strain-cyclicloading-Griggsapparatus" is the equivalent of the file described just above at a temperature of 400C. The text file "Vermont-antigorite-500C-1000MPa-stress-strain-cyclicloading-Griggsapparatus" is the equivalent of the file described just above at a temperature of 500C.
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This dataset contains raw (clean but not interpreted) triaxial compressive strength data of tests conductive at elevated pressure and temperature as outlined in "Vannucchi, P., Clarke, A., de Montserrat, A., Ougier-Simonin, A., Aldega, L., & Morgan, J. P. (2022). A strength inversion origin for non-volcanic tremor. Nature Communications, 13(1), 2311. https://doi.org/10.1038/s41467-022-29944-8". The data is provided in a .zip folder containing the files of 5 experiments that are accompanied by a README file for introduction. Files format is Microsoft Excel Worksheet (.xlsx) and data are tabulated. Each file contains the corresponding relevant sample’s details, and each column of data is clearly labelled, units included. For each experiment, time, axial force, axial displacement, axial stress, confining displacement, confining pressure, axial strain A and B, axial average strain, circumferential extensometer, circumferential strain, volumetric strain, internal temperature, and axial delta P were recorded. Triaxial testing was undertaken using the MTS 815 servo-controlled stiff frame inside a vessel capable of a confining pressure up to 140 MPa at the Rock Mechanics and Physics Laboratory, British Geological Survey, UK. The confining cell is fitted with external heater bands and utilizing utilizes cascade control from internal and external thermocouples (accurate to ± 0.5°C). An initial axial pre-load of 2.3 kN was applied, to ensure a stable contact and alignment of the platens. The confining pressure vessel was then closed and filled with mineral oil confining fluid. The axial pre-load was maintained whilst the confining pressure was applied at 2 MPa/min to 60 or 120 MPa; these values were chosen to approximately bracket the pressures at the up-dip limit of seismic nucleation, corresponding to 2 – 4 km depth (Arroyo et al., 2014). At this point, whilst held in axial force and confining pressure control, the rig was heated at 2°C/min to 60°C to approximate the average temperature conditions at the depth of the up-dip limit of seismic nucleation (Harris and Spinelli, 2010). The samples were then left for approximately 1 hour allowing thermal equilibrium to be reached throughout the confining fluid and the samples. Once stable, axial loading was initiated in constant axial strain rate control at a rate of 5.0 x 10-6 s-1 until macroscopic failure occurred or a significant amount of post peak-stress axial strain was recorded (between 2% and 5%). We note that one test was conducted at the higher temperature of T=120°C with a result within 2.5% of the strength at T=60°C (Table 1). As this is below the expected sample-to-sample variability, no further temperature studies were conducted. The axial load, axial load actuator displacement, axial stress (s1), differential stress (Q=s1 - s3), confining pressure Pc (= s2= s3), confining pressure actuator displacement, axial strain (eax), circumferential strain (ecirc) and temperature were monitored throughout at sampling frequencies of 1s and 0.5kN. File names are: YYYY-MM-DD_LabProjectNumber_SiteName-SampleNumber