ALBERT

Description: 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.

Description: 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.

Description: 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.

Description: This data set includes digital image correlation data from analog earthquakes experiments. The data consists of grids of surface strain and time series of surface displacement (horizontal and vertical) and strain. The data have been derived using a stereo camera setup and processed with LaVision Davis 10 software. Detailed descriptions of the experiments and results regarding the surface pattern of the strain can be found in Kosari et al. (in review), to which this data set is supplementary. We use an analog seismotectonic scale model approach (Rosenau et al., 2019 and 2017) to generate a catalog of analog megathrust earthquakes (Table 1). The presented experimental setup is modified from the 3D setup used in Rosenau et al. (2019) and Kosari et al. ( 2020). The subduction forearc model wedge is set up in a glass-sided box (1000 mm across strike, 800mm along strike, and 300 mm deep) with a dipping, elastic basal conveyor belt and a rigid backwall. An elastoplastic sand-rubber mixture (50 vol.% quartz sandG12: 50 vol.% EPDM rubber) is sieved into the setup representing a 240 km long forearc segment from the trench to the volcanic arc. The shallow part of the wedge includes a basal layer of sticky rice grains characterized by unstable stick-slip sliding representing the seismogenic zone. Stick-slip sliding in rice is governed by a rate-and-state dependent friction law similar to natural rocks. According to Coulomb wedge theory (Dahlen et al., 1984), two types of wedge configurations have been designed: a “compressional” configuration represents an interseismically compressional and coseismically stable wedge (compressional configuration), and a “critical” configuration, which is interseismically stable (close to critically compressional) and may reach a critical extensional state coseismically (critical configuration). In the compressional configuration, a flat-top (surface slope α=0) wedge overlies a single large rectangular in map view stick-slip patch (Width*Length=200*800 mm) over a 15-degree dipping basal thrust. In the critical configuration, the surface angle of the elastoplastic wedge varies from the coastal segment onshore (α=10) to the inner-wedge offshore (α=15) segments over a 5-degree dipping basal thrust. Slow continuous compression of the wedge by moving the basal conveyor belt at a speed velocity of 0.05 mm/s simulates plate convergence and results in the quasi-periodic nucleation of quasi-periodic stick-slip events (analog earthquakes) within the rice layer. The wedge responds elastically to these basal slip events, similar to crustal rebound during natural subduction megathrust earthquakes.

Description: This dataset provides friction data from ring-shear tests (RST) on twice broken rice used in the GEC Laboratory in CY Cergy Paris University in stick-slip experiments. They were obtained by Sarah Visage as part of her doctoral training (funded by the ANR DISRUPT programme) during an invitation at the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam. Like any granular material, the twice broken rice is characterized by several internal friction coefficients μ and cohesions C, classicaly qualified as dynamic, static, and reactivation coefficients. In adition, since the rice exhibits a stick slip behaviour, the various shear - velocity or shear-displacement curves exhibit high frequency oscillations and we therefore define maximum, minimum, and mean values corresponding respectively to the curve peaks, curve troughs and smoothed curve.

Description: This dataset provides friction data from ring-shear tests (RST) for wheat flour used as a fine-grained, cohesive analogue material for simulating brittle upper crustal rocks in the analogue labor-atory of the Institute of Geophysics of the Czech Academy of Science (IGCAS). It is 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 friction coefficients µP of the tested material is ~0.72, dynamic friction coeffi-cients µD is ~0.67 and reactivation friction coefficients µR is ~0.70. Cohesions of the material range between 27 and 50 Pa. The material shows a minor rate-weakening of ~1.5% per ten-fold change in shear velocity v and a stick-slip behaviour at low shear velocities.

Description: This dataset includes surface 3D stereoscopic Digital Image Correlation (3D stereo DIC) images and videos of 10 analogue models on crustal scale rifting with a rotational component. In addition, this dataset provides CT imagery of four analogue models that have been analyzed by means of Digital Volume Correlation (DVC) applied on X-Ray computed tomography volumes. Data of CT scanned models also includes slices of the volumetric displacement set for each displacement component. Using a brittle-viscous two-layer setup, the experiments focused on surface rift propagation, internal viscous flow driven by a horizontal pressure gradient and the interaction of internal and surface deformation. All experiments were performed at the Tectonic Modelling Laboratory of the University of Bern (UB). 3D stereo DIC analyses were performed at the GFZ German Research Centre for Geosciences (GFZ) and DVC analyses were performed at the Royal Holloway University London (RHUL). All models consist of a two-layer brittle-viscous set up with a total thickness of 6 cm. Thickness variations in brittle and ductile layers are expressed by the ratio RBD = brittle layer thickness/ductile layer thickness, which ranges from RBD = 0.5 to RBD = 2. The model set up lies on top of a 5 cm thick foam base with a trapezoidal shape with a height of 900 mm and a pair of bases with widths of 310 mm and 350 mm at the far ends, respectively. The foam block is sliced into segments such that 7 interlayered 0.5 cm thick plexiglass bars prevent foam collapse under the model weight. Before model construction, the foam-plexiglass assemblage is placed between longitudinal side walls. The experimental set-up is such that rotational extension in one part of the model domain is separated from rotational shortening in the other part of the model domain by a vertical rotation axis (Fig. 1). During the model run, the foam homogeneously expands in the domain undergoing extension and homogeneously contracts in the domain undergoing shortening. The applied velocity for all models is 10 mm/h and refers to the divergence of the sidewalls furthest away from the rotation axis which decreases linearly towards the rotation axis. This results in a maximum displacement of 40 mm at the outermost circular segment after a total run time of 4h.

Description: This data set includes data derived from high-speed surface displacement observations from analog earthquake experiments. The data consists of surface displacement of the experiment upper plate and slab, slip distribution, and grids of Coulomb Failure Stress (CFS). The surface displacement observations have been captured using a highspeed CMOS (Complementary Metal Oxide Semiconductor) camera (Phantom VEO 640L camera, 12 bit) and processed with LaVision Davis 10 software. Description of the experiments and results regarding the surface displacement observation, Slip distribution, and CFS can be found in Kosari et al. (2022), to which this data set is supplementary. We use an analog seismotectonic scale model approach (Rosenau et al., 2019 and 2017) to generate a catalog of analog megathrust earthquakes. The presented experimental setup is modified from the 3D setup used in Rosenau et al. (2019) and Kosari et al. ( 2020 and 2022). The subduction forearc model wedge is set up in a glass-sided box (1000 mm across strike, 800mm along strike, and 300 mm deep) with a dipping, elastic basal conveyor belt, and a rigid backwall. An elastoplastic sand-rubber mixture (50 vol.% quartz sandG12: 50 vol.% EPDM rubber) is sieved into the setup representing a 240 km long forearc segment from the trench to the volcanic arc. The shallow part of the wedge includes a basal layer of sticky rice grains characterized by unstable stick-slip sliding representing the seismogenic zone. The Stick-slip sliding in rice is governed by a rate-and-state dependent friction law similar to natural rocks. A flat-top (surface slope α=0) wedge overlies rectangular stick-slip patch/es over a 15-degree dipping basal thrust. Two different seismic configurations of the shallow part of the wedge base (the megathrust) represent the depth extent of the seismogenic zone in nature. In the first configuration (homogeneous configuration), a single large rectangular stick-slip patch (Width*Length=200*800 mm) is implemented as the main slip patch (MSP). In the second case (heterogeneous configuration), two square-shaped MSPs (200*200mm) have been emplaced, acting as two medium-size seismogenic asperities surrounded by a salt matrix hosting frequent small events. Slow continuous compression of the wedge by moving the basal conveyor belt at a speed velocity of 0.05 mm/s simulates plate convergence and results in the quasi-periodic nucleation of quasi-periodic stick-slip events (analog earthquakes) within the sticky-rice layer. The wedge responds elastically to these basal slip events, similar to crustal rebound during natural subduction megathrust earthquakes.

Description: Understanding the along-strike seismogenic behavior of megathrusts is crucial to anticipating seismic hazards in subduction zones. However, if and how spatiotemporal frictional heterogeneity (high and low kinematic coupling) at depth feeds back into the upper-plate deformation pattern and how the upper-plate elastic signals and permanent records may correlate have yet to be fully understood. Hence, we mimic subduction megathrust seismic cycles using an analog seismotectonic model of an elastoplastic wedge overlying a frictionally heterogeneous megathrust. Coseismically, the zone above the down-dip limit of the aseismic and seismogenic patches undergoes extension and contraction, respectively, while the strain state shows a switch in polarity from coseismic to interseismic. The down-dip limit of the creeping zone produces permanent along-strike extension or contraction, depending on the frictional barrier strength. Our experiments show that the frictional locking heterogeneity generates more segmented along-strike strain patterns elastically (short term) than permanently (long term). Moreover, our results suggest that along-strike upper-plate strain patterns could serve as a proxy for interpreting persistent lateral variations of seismogenic behavior in subduction megathrusts.

Description: This data set is digital image correlation data, including surface displacement and strain data from laboratory subduction megathrust earthquake cycles. The data consists of grids of surface strain (elastic and permanent), trench-normal surface displacement, vorticity and divergence maps over analog seismic cycles, and time series of surface displacement. The data have been derived using a stereo camera setup and processed with LaVision Davis 10 software. Detailed descriptions of the experiments and results regarding the surface pattern of the strain can be found in Kosari et al. (2023), to which this data set is supplementary. We use three configurations to mimic the along-strike heterogeneous spatiotemporal distribution of frictional locking (Rosenau et al., 2019; Kosari et al., 2022b). A central patch separates two stick-slip zones as an aseismic barrier in all configurations. The frictional properties of the central patch vary as a velocity-strengthening (VS configuration), a velocity-neutral (VN), and a velocity-weakening (VW configuration). The VW zone generates smaller slip events with a higher frequency (i.e., recurrence interval) than the stick-slip zones. Four frictionally different materials have been emplaced on the interface: The sticky-rice as velocity-weakening material (a-blt;0) resulting in stick-slip cycles simulating earthquake cycles, fine-grained sugar and rubber-sand mixture as velocity-strengthening (a-bgt;0) and velocity-neutral (a-b=0) material, and fine-grained salt as velocity-weakening material (a-blt;0) (Kosari et al., 2023).