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Supplement to “Synchronization of great subduction megathrust earthquakes: Insights from scale model analysis”

This data set provides data from subduction zone earthquake experiments and analysis described in Rosenau et al. (2019). In the experiments analogue seismotectonic scale models of subduction zones characterized by two seismogenic asperities are used to study the interaction of asperities over multiple seismic cycles by means of static (Coulomb failure) stress transfer. Various asperity geometries (lateral/along-strike of the subduction zone distance and vertical/across-strike of the subduction zone offset) are tested on their effect on recurrence pattern of simulated great (M8+) earthquakes.The results demonstrate the role of stress coupling in the synchronization of asperities leading to multi-asperity M9+ events in nature. The data set contains time series of experimental surface velocities from which analogue earthquakes are detected and classified into synchronized events and solo events. The latter are subcategorized into main events and aftershocks and into normal and thrust events. An analogue earthquake catalogue lists all categorized events of the 12 experiments used for statistical analysis. Moreover, results from elastic dislocation modelling aimed ate quantifying the stress coupling between the asperities for the various geometries are summarized. Basic statistics of classified events (e.g. percentage of categorized events, coefficient of variation in size and recurrence time etc.) are documented. Matlab scripts are provided to visualize the data as in the paper.

Rheology of PDMS-corundum sand mixtures from the Tectonic Modelling Lab of the University of Bern (CH)

This dataset provides rheometric data of silicone (Polydimethylsiloxane, PDMS SGM36)-corundum sand mixtures used for analogue modelling in Zwaan et al. (2016, 2017), Zwaan and Schreurs (2017) and in the Tectonic Modelling Lab of the Institute of Geological Sciences at the University of Bern (CH). The PDMS is produced by Dow Corning and its characteristics have been described by e.g. Rudolf et al. (2016a,b). The corundum sand (Normalkorund Braun 95.5% F120 by Carlo Bernasconi AG: https://www.carloag.ch/shop/catalog/product/view/id/643), has a grainsize of 0.088-0.125 mm and a specific density of 3.96 g cm^-3. Further rheological characteristics are described by Panien et al. (2006). The density of the tested materials ranges between 1 (pure PDMS) and 1.6 g cm^-3 (increasing corundum sand content in mixture). The material samples have been analysed in the Helmholtz Laboratory for Tectonic Modelling (HelTec) at GFZ German Research Centre for Geosciences in Potsdam using an Anton Paar Physica MCR 301 rheometer in a plate-plate configuration at room temperature. Rotational (controlled shear rate) tests with shear rates varying from 10^-4 to 10^-1 s^-1 were performed.According to our rheometric analysis, the material is quasi Newtonian at strain rates below 10^-3*s^-1 and weakly shear rate thinning above. Viscosity and stress exponent increase systematically with density from ~4*10^4 to ~1*10^5 Pa*s and from 1.06 to 1.10, respectively. A first application of the materials tested can be found in Zwaan et al. (2016). Detailed information about the data, methodology and a list of files and formats is given in the "data description" and "list of files" that are included in the zip folder and also available via the DOI landing page.

RST Evaluation - Scripts for analysing shear experiments from the Schulze RST.pc01 ring shear tester

The software RST Evaluation is a series of scripts to semi-automatically evaluate shear experiments done at the Helmholtz Laboratory for Tectonic Modelling. In principle, it may be used for other measurements done in a similar setup, but it was build with our standardized workflow in mind. The shear experiments are done in a ring shear type shear cell rst.pc01 manufactured by D. Schulze (Details in ASTM standard D-6773). It uses an easy and reproducible workflow to determine yield properties, cohesion and dilational properties of a granular bulk material, such as sand or glass beads.

Rheology of viscous materials from the CNR-IGG Tectonic Modelling Laboratory at the University of Florence (Italy)

This dataset provides rheometric data of three viscous materials used for centrifuge experiments at the Tectonic Modelling Laboratory of CNR-IGG at the Earth Sciences Department of the University of Florence (Italy). The first material, PP45, is a mixture of a silicone (Polydimethylsiloxane or PDMS SGM36) and plasticine (Giotto Pongo). The PDMS is produced by Dow Corning and its characteristics are described by e.g. Rudolf et al. 2016a,b). Giotto Pongo is produced by FILA (Italy). Both components are mixed following a weight ratio of 100:45, and the final mixture has a density of 1520 kg m3. The second material, SCA705 is a mixture of Dow Corning 3179 putty, mixed with fine corundum sand and oleic acid with a weight ratio of 100:70:05 and a resulting density of 1660 kg m3. The final material, SCA7020 consists of the same components as SCA705, but with a slightly higher oleic acid content reflected in the weight ratio of 100:70:20. The mixture’s density is 1620 kg m3. The material samples have been analyzed in the Helmholtz Laboratory for Tectonic Modelling (HelTec) at GFZ German Research Centre for Geosciences in Potsdam using an Anton Paar Physica MCR 301 rheometer in a plate-plate configuration at room temperature (20˚C). Rotational (controlled shear rate) tests with shear rates varying from 10-4 to 1 s-1 were performed. Additional temperature tests were run with shear rates between 10-2 to 10-1 s-1 for a temperature range between 15 and 30˚C. According to our rheometric analysis, the materials all exhibit shear thinning behavior, with high power law exponents (n-number) for strain rates below 10-2s-1, while power law exponents are lower above that threshold.For PP45, the respective n-numbers are 4.8 and 2.6, for SCA705 6.7 and 1.5, and for SCA7020 9.1 and 2.0. The temperature tests show decreasing viscosities with increasing temperatures with rates of -3.8, -1.4 and -1.9% per ˚K for PP45, SCA705 and SCA7020, respectively. An application of the materials tested can be found in Zwaan et al. (2020).

Particle image velocimetry data from seismotectonic analog models focusing on the role of seamount subduction on megathrust seismicity

This dataset provides the surface velocity fields derived with MatPIV (open-source Matlab toolbox for Particle Image Velocimetry; Sveen 2004) of three seismotectonic analog models (e.g., Rosenau et al., 2017) performed to investigate the role of geometry and friction of a single subducting seamount on the seismogenic behavior of the megathrust. Model 1 has a seamount covered by sandpaper (i.e., high friction) that is placed at 1/2 of the trench-parallel length of the seismogenic zone. Model 3 has the same geometry of model 1, but the seamount is in direct contact with the gelatin (i.e., not covered by sandpaper, hence low friction). Model 5 has a low friction patch (i.e., no geometry) that is placed again at 1/2 of the trench-parallel length of the seismogenic zone. Together with the surface velocity fields, we also provide Matlab scripts for visualization. A more detailed description of the experimental setup, configuration of the models and materials can be found in Menichelli et al. (submitted), to which this dataset is supplementary. Our seismotectonic models represent a downscaled subduction zone (1 cm in the model corresponds to 6.4 km in nature; Rosenau et al., 2017). The experimental setup consists of a 60 x 34 cm2 Plexiglass box with a 10°-dipping aluminum basal plate that moves downward with a constant velocity of 0.01 cm/s, analog of the subducting plate. The overriding plate is represented by an elastic wedge of 2.5 wt% pigskin gelatin at T = 10 °C (Di Giuseppe et al., 2009). The seismogenic zone of the megathrust is simulated using a rectangular sandpaper patch (Corbi et al., 2013), with a downdip width of 16 cm and located 31 and 47 cm from the backstop. This corresponds to a 100-km-wide seismogenic zone extending over a depth interval between 15 and 34 km. The updip and down dip aseismic regions of the megathrust are simulated by plastic sheets that are fixed on the setup frame and not subject to subduction (Corbi et al., 2013). A 3D-printed PLA seamount is placed on the seismogenic zone (e.g., Van Rijsingen et al., 2019). The seamount has a height of 6.28 mm and a diagonal length of 94 mm, corresponding to 4 km and 60 km in nature, respectively. These dimensions scale well-known seamounts, such as the Joban Seamount chain in the Japan Trench or the Louisville seamount chain in the Tonga-Kermadec Trench. Experiments were monitored with a CCD camera that acquired a sequence of high-resolution top-view images (1600 x 1200 pixels2, 8 bit, 256 gray levels) at 7.5 fps for the entire duration of the experiment (i.e., ca. 24 minutes). Images are processed with Particle Image Velocimetry (PIV; Adam et al., 2005) using the open-source Matlab toolbox MatPIV (Sveen, 2004). MatPIV provides the velocity field between two consecutive frames, measured at the surface of the model. The velocity field was then used as input to identify analog seismic events using the open-source Matlab function findpeak. The threshold used was 0.1 cm/s. Once earthquakes were identified, we derived their source parameters such as seismic slip, magnitude, and recurrence time following Corbi et al. (2017) and van Rijsingen et al. (2019).

Granular Healing - Python module associated to the 2022 GeoMod material benchmark

The software is provided as an executable python module. The software automatically analyzes the files present in the data publication. The results are saved in the form of the images presented in the main publication. Each figure is implemented as a dedicated function that first loads the necessary data, then does some processing steps, such as curve fitting, and then plots the outputs in the desired layout. A 'main' function calls all figure functions sequentially. However, the packages is modular so that each individual plot has a standalone function which could be used with other, similarly structured data. Several submodules provide additional data for plotting, e.g. the 'groups' submodule that contains naming schemes and the densities for all samples.

Ring-shear test data of quartz sand from the Tectonic Modelling Lab of the University of Bern (CH)

This dataset provides internal and basal (wall) friction data from ring-shear tests (RST) on a quartz sand material that has been used in tectonic experiments in Zwaan et al. (2016, 2017), Zwaan and Scheurs (2017) and in the Tectonic Modelling Lab of the University of Bern (CH) as an analogue for brittle layers in the crust or lithosphere. The material has been characterized by means of internal and basal friction coefficients μ and cohesions C as a remote service by the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam for the Tectonic Modelling Lab of the University of Bern (UB).According to our analysis the material behaves as a Mohr-Coulomb material characterized by a linear failure envelope. Internal peak, dynamic and reactivation friction coefficients are μP = 0.73, μD = 0.61, and μR = 0.66, respectively. Internal cohesions C are in the range of 10 to 70 Pa. Basal peak, dynamic and reactivation friction coefficients are μP = 0.41, μD = 0.35, and μR = 0.36, respectively, whereas basal cohesions C are in the range of 120 to 150 Pa. The rate dependency of the internal dynamic friction coefficient is insignificant (<1%).

A database of centrifuge analogue models testing the influence of inherited brittle fabrics on continental rifting

This dataset presents the raw data of an experimental series of analogue models performed to investigate the influence of inherited brittle fabrics on narrow continental rifting. This model series was performed to test the influence of brittle pre-existing fabrics on the rifting deformation by cutting the brittle layer at different orientations with respect to the extension direction. An overview of the experimental series is shown in Table 1. In this dataset we provide four different types of data, that can serve as supporting material and for further analysis: 1) The top-view photos, taken at different steps and showing the deformation process of each model; they can be used to interpret the geometrical characteristics of rift-related faults; 2) Digital Elevation Models (DEMs) used to reconstruct the 3D deformation of the performed analogue models, allowing for quantitative analysis of the fault pattern. 3) Short movies built from top-view photos which help to visualize the evolution of model deformation; 4) line-drawing of fault and fracture patters to be used for fault statistical quantification. Further details on the modelling strategy and setup can be found in Corti (2012), Maestrelli et al. (2020), Molnar et al. (2020), Philippon et al. (2015), Zwaan et al. (2021) and in the publication associated with this dataset. Materials used for these analogue models were described in Montanari et al. (2017) Del Ventisette et al. (2019) and Zwaan et al. (2020).

Supplement to: Sandbox Rheometry: Co-Evolution of Stress and Strain in Riedel- and Critical Wedge-Experiments

This dataset is supplementary to the article of Ritter et al. (2017). In this article, a new experimental device is presented that facilitates precise measurements of boundary forces and surface deformation at high temporal and spatial resolution. This supplementary dataset contains the measurement data from two experiments carried out in this new experimental device: one experiment of an accretionary critical wedge and one of Riedel-type strike-slip deformation. For a detailed description of the set-up and an analysis of the data, please see Ritter et al. (2017).The data available for either experiment are:• A video showing deformation in top view together with the evolution of boundary force. This file is in AVI-format.• A time-series of 2D vector fields describing the surface deformation. These vector fields were obtained from top-view video images of the respective experiment by means of digital image correlation (DIC). Each vector field is contained in a separate file; the files are consecutively numbered. The vector fields are stored in *.mat-files that can be opened using e.g. the software Matlab or the freely available GNU Octave. They take the form of Matlab structure arrays and are compatible to the PIVmat-toolbox by Moisy (2016) that is freely available. The most important fields of the structure are: x and y, that are vectors spanning a coordinate system, and vx and vy, which are arrays containing the actual vector components in x- and y-direction, respectively.• A file containing the measurements of the boundary force applied to drive deformation. This file is also a *.mat-file, containing a structure F with fields force, velocity and position. These fields are vectors describing the force applied by the indenter, the indenter velocity and the indenter position

LSMOD.1 - Global paleomagnetic field model for 50 -- 30 ka BP

Global spherical harmonic paleomagnetic field model LSMOD.1 describes the magnetic field evolution from 50 to 30 ka BP based on published paleomagnetic sediment records and volcanic data. The time interval includes the Laschamp (~41 ka BP) and Mono Lake (~34 ka BP) excursions. The model is given with Fortran source code to obtain spherical harmonic magnetic field coefficients for individual epochs and to obtain time series of magnetic declination, inclination and field intensity from 49.95 to 30 ka BP for any location on Earth. For details see M. Brown, M. Korte, R. Holme, I. Wardinski and S. Gunnarson (2018): Earth's magnetic field is probably not reversing. PNAS, 115, 5111-5116.

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