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Digital Volume Correlation (DVC) data from an analogue experiment exploring kinematic coupling of brittle and viscous deformation

This dataset includes volumetric data sets from a Digital Volume Correlation (DVC) analysis for recreating images of a re-analyzed analogue models previously presented in (Zwaan et al., 2018). Using a brittle-viscous two-layer setup, this experiment focused on the evolution of a rift-pass structure. On top of the viscous layer, two viscous seeds are placed with a right-stepping stair-case offset to simulate two propagating rift segments, confining a central rift-pass block (Fig. 1). The selected model was analyzed by means of Digital Volume Correlation (DVC) applied on X-Ray computed tomography (XRCT) volumes. The data set includes DVC data in the form of .mat files for incremental (i.e., 20 min intervals) and cumulative displacement components. In addition, this dataset provides a MATLAB script for 1) recreating volumetric displacement sets of subsequent time steps 2) calculating finite stretches and 3) rigid-body rotations. The used experiment was performed at the Tectonic Modelling Laboratory of the University of Bern (UB). DVC analysis was performed at the Royal Holloway University London (RHUL). The model consists of a two-layer brittle-viscous set up with a total thickness of 8 cm and the set up lies on top of a 5 cm thick foam-plexiglass base with a length and width of 800 mm by 305 mm, respectively. Before model construction, the foam-plexiglass assemblage is placed between longitudinal side walls and expands during the course of the experiment as the mobile sidewalls move apart. The applied divergence velocity is 7.5 mm/h and with has an orthogonal direction with respect to the viscous seeds. This results in a maximum displacement of 30 mm after a total run time of 4h. Detailed descriptions of the experiment, mechanical properties as well as monitoring techniques can be found in Schmid et al. (2024).

3D stereo DIC data from analogue models exploring fault growth and rift propagation in rotational rift systems

This dataset includes surface 3D stereoscopic Digital Image Correlation (3D stereo DIC) images and videos of 9 analogue models on crustal scale rifting with a rotational component. Using a brittle-viscous two-layer setup, the experiments focused on near-surface fault growth, rift segment interaction and rift propagation. All experiments were performed at the Tectonic Modelling Laboratory of the University of Bern (UB). All models consist of a two-layer brittle-viscous set up with a total thickness of 6 cm. Thickness variations in ductile and brittle layers are expressed by the ratio RBD = brittle layer thickness/ductile layer thickness, which ranges from RBD = 1 to RBD = 3. 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 of 310 mm and 350 mm. The foam block is sliced into segments such that 7 interlayered 0.5 cm thick plexiglass bars prevent foam collapse under the model weight. The foam base is initially compressed between the longitudinal side walls and homogeneously expands during the rotational opening. Applied velocities refer to the divergence of the sidewalls at the outermost point (i.e., furthest away from the rotation axis) and decrease linearly towards the rotation axis. These velocities vary from 10 mm/h over a total run time of 4 h up to 40 mm/h over a total run time of one hour, resulting in identical total extension of ca 13% (given an initial model width of 31 cm) for all models. Detailed descriptions of the experiments as well as monitoring techniques can be found in Schmid et al. (2021).

DVC and 3D stereo DIC data from analogue models exploring interaction of viscous flow and surface deformation in rotational rift systems

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.

Centrifuge models investigating the influence of transverse pre-existing weaknesses on continental rifting

We present the results of centrifuge experiments investigating the role of preexisting crustal discontinuity on continental rifting. Specifically, we reproduce inherited weaknesses, orthogonal to the rift trend and parallel to the extension direction, and analyze their influence on the evolution and architecture of extensional deformation in the inner part and at the margins of continental rift valleys. Four different models, with variable width of the pre-existing weakness are illustrated.The models show a significant influence exerted by the pre-existing anisotropy on rifting: specifically, the inherited weakness inhibits the development of large boundary faults at rift margins, which are instead replaced by gentle monoclines dipping toward the rift axis. Axial faults are “captured” by the inherited anisotropy and rotate towards the pre-existing weakness, which therefore produces an unusual structural pattern also in the axial zone. This influence is dependent on the initial width of the pre-rift anisotropy and becomes negligible when its scaled width is 20 km or less.

Laptev Sea Rift Seismological Network (SIOLA) Part I

The Laptev Sea region is one of the very few places on Earth where mid-ocean spreading centres continue into continental rift zones. The Gakkel Ridge, the active spreading centre in the Eurasia Basin of the Arctic Ocean, is characterized by well-defined seismicity close to its axial graben. In contrast below the Laptev Sea Shelf, which consists of a series of sediment filled grabens (500 km wide, 700 km long), only more diffuse seismic activity is observed. The pre-rift basement in the Laptev Sea is most probably formed by Late-Paleozoic and Late-Mesozoic fold belts. The Laptev Rift Basin is filled with Upper Cretaceous and Cenozoic sediments of variable thickness (1.5 to 14 km). The westernmost limit of seismicity is located close to edge of thick lithosphere of the Siberian Shield, which indicates some structural control on the recent tectonic activity. Focal depths are mainly less than 25 km (continent) and less than 10 km (ocean). Sparse observations of upper mantle earthquakes are under debate. The pole of rotation is very close to the study area, most probably to the south of Lena delta. Existing data indicate changes between compressional and extensional tectonic phases over short distances. This might be a consequence of the fact that the pole of rotation is close to our study area. The Khatanga-Lomonosov Shear Zone marks the border between the Gakkel Ridge and Laptev Sea Rift System, but its nature and extent are debated. Crustal extension seems to be concentrated in the eastern Laptev Sea area. Fault plane solutions are sparse and mostly not well determined to describe the movements in greater detail. Thus, with this project we intend to investigate details on tectonic movements in the Laptev Sea to better describe this amagmatic rifting and its consequences in an Arctic and global context. In general, we intend to increase the number of seismological stations for monitoring local earthquakes in the Laptev Sea/Lena delta region to fulfil the following objectives: (1) Location of microseismicity and its relationship with active faults. We want to identify seismologically active faults zones. In a first step we like to deploy instruments in earthquake areas, which are already identified by the global seismological network, though with low spatial resolution.(2) Focal mechanisms. What is the present geodynamic setting, where is extension and where is compression in the Laptev Sea and in the Lena delta region, where is the exact pole of rotation? What is the relation of the recent seismicity to pre-existing crustal and lithosphere structures (e.g., western Verkhoyansk Fold-and-Thrust Belt/Olenek Zone or South Anyui Suture)?(3) Lithosphere structure. It is interesting to note that despite the Cenozoic continental rifting in the Laptev Sea little volcanism is known. Thus, we like to compare the deep crustal and upper mantle structure with other continental rift systems (e.g. Afar) to enhance our understanding on the driving forces. The experiment is planned as a combination of stationary array(s) and moving small networks. Small networks are planned to operate for 1-2 years at one location before it will be moved to another. Waveform data are available from the GEOFON data centre, under network code 8B.

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