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TS9.1

EDI
Analogue and numerical modelling of tectonic processes

Geologic processes are generally too slow, too rare, or too deep to be observed in-situ and to be monitored with a resolution high enough to understand their dynamics. Analogue experiments and numerical simulation have thus become an integral part of the Earth explorer's toolbox to select, formulate, and test hypotheses on the origin and evolution of geological phenomena.

To foster synergy between the rather independently evolving experimentalists and modellers we provide a multi-disciplinary platform to discuss research on tectonics, structural geology, rock mechanics, geodynamics, volcanology, geomorphology, and sedimentology.

We therefore invite contributions demonstrating the state-of-the-art in analogue and numerical / analytical modelling on a variety of spatial and temporal scales, varying from earthquakes, landslides and volcanic eruptions to sedimentary processes, plate tectonics and landscape evolution. We especially welcome those presentations that discuss model strengths and weaknesses, challenge the existing limits, or compare/combine the different modelling techniques to realistically simulate and better understand the Earth's behaviour.

Co-organized by GD9/GM9
Convener: Frank ZwaanECSECS | Co-conveners: Valentina Magni, Michael RudolfECSECS, Ágnes KirályECSECS, Fabio Corbi
Presentations
| Tue, 24 May, 15:10–18:24 (CEST)
 
Room D1

Tue, 24 May, 15:10–16:40

Chairpersons: Frank Zwaan, Ágnes Király, Valentina Magni

15:10–15:12
Introduction - Block 1

15:12–15:22
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EGU22-356
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ECS
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solicited
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Highlight
Antoine Auzemery

Modelling studies show that subduction initiation requires failure of the load-bearing crustal and mantle layers and critically depends on the buoyancy and strength contrast within the lithosphere. Such findings suggest that the probability of subduction initiation must increases in the vicinity of continental margins. Yet, direct evidence for subduction initiation at passive margin is scarce and the mechanisms of subduction initiation in this particular setting remains a recurrent and long-standing unresolved question. Therefore, our study focuses on the kinematic and rheologic key parameter combinations relevant for the formation of a subduction zone, with the aim of identifying the feasibility of subduction initiation at a passive margin setting. To challenge the existing limits and discriminate processes that fit conditions for subduction nucleation, we compare and combine analogue and numerical modelling techniques. In this work, numerical modelling allows exploring temperature driven feedback mechanisms whereas analogue modelling allows for mapping characteristic length scales of deformation against the mode of subduction initiation. Overall, model results highlight that the convergence rate, the strength contrast at the margin as well as the degree of crust-mantle coupling control the development of a shear zone at the base of the crust, and the propagation of deformation into the mantle lithosphere. In addition, comparison between analogue and numerical modelling results infers that shear heating, weak sediments, magmatic heterogeneities or a serpentinite mantle wedge, are important parameters for the development of a self-sustaining subduction zone. The relevance of the modelling results is demonstrated by comparing length-scales of deformation with observations from inverted continental passive margins and orogenic systems, such as the Alps and Dinarides. Models predict that primary response of the lithosphere to compression is by folding and that tectonic structures and early-stage length-scales of deformation can be used to predict the likeliness of subduction initiation at a passive margin.

How to cite: Auzemery, A.: A comparison of numerical and analogue models of subduction initiation at passive margins., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-356, https://doi.org/10.5194/egusphere-egu22-356, 2022.

15:22–15:23
Questions - 1 min

15:23–15:28
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EGU22-7095
Benjamin Guillaume and Guido Gianni

Cases where multiple tectonic regimes acted closely in space and time have been long recognized. The coexistence of thrust, strike-slip, and normal faulting has been documented in thick orogenic regions, in oblique convergent settings associated with strain partitioning, in areas of indentation tectonics and lateral escape, and synorogenic foreland rifting/transtension settings, where extension-transtension takes place in close spatiotemporal relation with plate-margin shortening. Here, we use analogue models to test how parameters like the crustal strength, basement inheritances, and relative rate of extrusion/indentation can be effective mechanisms to explain the coeval emplacement of thrust, strike-slip, and normal faults. We also investigate their effect on fault reactivation in previously extended basins.

We show that a strong crust can exhibit coeval thrust faults, strike-slip faults and normal faults for ratios of extrusion over indentation rates in between 1.4 and 2, as orientation and magitude of principal stresses spatially vary within the model. For a weaker crust, normal faults and thrusts faults cannot coexist at the same time. Inheritance, which is implemented through the presence of a seed simulating a preexisting weakness zone or through an initial phase of extension, controls the geometry of strike-slip faults, whose orientation departs from the Coulomb fracture criterion. Reactivation of former normal faults as normal faults is only possible for ratios of extrusion over indentation rates over 1, for both weak and strong crusts. For lower rates, pre-existing normal faults are reactivated as indentation-parallel strike-slip faults. Our experimental results are then compared with the tectonic evolution of the Eastern Anatolia, the Alps and the Central Patagonia.

How to cite: Guillaume, B. and Gianni, G.: Control of inheritance, crustal strength and relative rate of extrusion/indentation on 3D strain distribution and basin reactivation: insights from laboratory models , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7095, https://doi.org/10.5194/egusphere-egu22-7095, 2022.

15:28–15:29
Questions - 1 min

15:29–15:34
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EGU22-11360
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ECS
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Bianca Copot et al.

Thin-skinned fold and thrust belts present exploration challenges in many places worldwide. The presence of multiple detachments in the stratigraphic sequence also adds to the complexity of such fold and thrust belts. This study aims to understand more about the effects of multiple detachments in thin-skinned fold and thrust belts through scaled analogue modelling experiments. Our main area of interest is Romania's prolific onshore hydrocarbon area, the foreland of the Eastern Carpathian Bend Zone. Here, one of the large uncertainties is if the Oligocene to lower Miocene strata experienced any shortening before salt deposition. If so, what would be the difference in the observed geometries?

Scaled sandbox models with layered brittle and ductile materials were used to gain critical insights into the structural evolution of this fold and thrust belt (ECBZ) and to reduce the above-mentioned uncertainties. The materials used in these experiments are: coloured dry quartz sand (for modelling brittle behaviour), silicone (for ductile behaviour of the salt), 200-300 μm glass microspheres and a mixture of silicone and granular materials (for the other detachment levels).

The experimental setup consists of a computerized deformation device that pulls a mobile plate at a constant rate beneath a fixed deformation box with one glass sidewall, one end of the box acting as a static buttress. Deformation monitoring has been achieved using top-view 3D digital image correlation techniques (DPIV- Digital Particle Image Velocimetry). The models were serially sectioned and photographed after post-experiment treatment (wetting and consolidation). The sections were used to build and interpret 3D digital models of the experiments.

Duplex structures mainly characterize the deformation in the sub-silicone. Some particular geometries observed in the sub-silicone (salt) sequence are buckle folds and lift-off folds. These mainly occur when the detachments within the sub-silicone mechanical stratigraphy consist of silicone/granular mixture. Although not traditionally interpreted and observed in the area, these results raise the possibility of alternative interpretations. The supra-silicone (salt) deformation is less complex, characterized by both fore- and backthrusts, most of them initiating as detachment folds, similar to what is seen in our area of interest.

Experimental results reduce exploration uncertainties by bringing more insights into the control and effects of multiple detachments on the structural development of fold and thrust belts. These modelling results also bring new possible interpretations in areas poorly constrained by seismic and well data.

How to cite: Copot, B., Tamas, D. M., Tamas, A., Krezsek, C., Schleder, Z., Lapadat, A., and Filipescu, S.: Effects of multiple detachments in thin-skinned fold and thrust belts: insights from analogue modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11360, https://doi.org/10.5194/egusphere-egu22-11360, 2022.

15:34–15:35
Questions - 1 min

15:35–15:40
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EGU22-10624
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ECS
Anindita Samsu et al.

Analogue models are powerful tools for investigating extensional and convergent tectonic processes in 4D and at multiple scales. However, rarely do we introduce two successive phases of tectonism in a single analogue experiment to study the interaction between structures from two kinematically distinct tectonic events. Here we showcase a series of analogue experiments in which lithospheric-scale models are extended and subsequently shortened, simulating rifting followed by inversion and mountain building.

In our experiments, we simulate rifting by extending a multi-layer, brittle-ductile model lithosphere; this initial model is analogous to a hot, thickened lithosphere immediately after orogenesis. We demonstrate that the absence or presence of a narrow, pre-existing weakness in the lithospheric mantle results in end-member models of either wide or narrow rifting, respectively. Extension is immediately followed by shortening of the model, where we observe that contractional structures are localised along pre-existing rift basins. Analyses of particle imaging velocimetry (PIV) data reveal that shortening is accommodated by several mechanisms, including reverse reactivation of normal faults and buckling and/or inversion within pre-existing basins. We also show that these findings are consistent with field and geophysical observations from northern Australia as well as previous numerical experiments.

How to cite: Samsu, A., Betts, P., Amirpoorsaeed, F., Cruden, A., and Gorczyk, W.: Stretch and fold: Multistage analogue experiments of rifting, inversion, and orogenesis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10624, https://doi.org/10.5194/egusphere-egu22-10624, 2022.

15:40–15:41
Questions - 1 min

15:41–15:46
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EGU22-11517
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ECS
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Tan Shu et al.

The ribbon-like Altai accretionary sedimentary wedge, representing the SW exteriors of the the Tuva-Mongol Orocline, suffered important Devonian and Permian deformation, metamorphism and melting. The last Permian deformation was associated with massive lower crustal melting, granulitization and lateral lower crustal flow of anatectic material. This lateral transfer was controlled by upwelling of the mantle below the extended parts of the crust. The subsequent Permian shortening led to development of a series of crustal scale detachment folds cored by migmatite-magmatite complexes and surrounded by weakly metamorphosed rocks in marginal synforms.

 

The current study aims to understand the geometry, kinematics and dynamics of such large scale folding in the Chinese Altai during compression of thermally softened crust confined in the Tuva-Mongol Orocline. In such a setting, the angle of convergence is progressively increasing during collision, as the curvature of the orocline increases. To visualize and quantify this process, we employed analog modeling by using paraffin wax for ductile lower crust and sand-cenosphere mixture for brittle upper crust. The model domains (60cm×70cm×3cm) are preheated for 15 hours to attain a stable initial thermal and rheological gradient. The base of the models sustains the temperature at 51 °C (the melting point for the paraffin wax) while the top part of the model is heated to 48 °C by convective air. Strain in the models is quantified from the top view using the stereoscopic digital image correlation system from Lavision GmbH. The models are shortened by movement of indenter wall driven by a step-motor. Three series of experiments were designed to simulate the above detachment folds. In the first series of models, the indenter wall is perpendicular to the shortening direction. In the second scenario, the indenter wall is initially obliquely oriented to the shortening direction. As for last scenario, the angle of convergence α (defined as the angle between the plate motion vector and the plate boundary) is continuously increased from initial 60° to 90°. This last mode mimics the effect of the closing orocline confining the thermally softened crust. All models display progressive development of an array of folds with crestal grabens that are cored by molten and partially molten wax. We describe how the style of folding, degree of strain partitioning and distribution of transcurrent movements differ between the modes of convergence.

How to cite: Shu, T., Závada, P., Krýza, O., Jiang, Y., and Schulmann, K.: Large scale detachment folding of thermally softened crust within a closing orocline in the Chinese Altai - insights from analog modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11517, https://doi.org/10.5194/egusphere-egu22-11517, 2022.

15:46–15:47
Questions - 1 min

15:47–15:52
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EGU22-1970
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ECS
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Timothy Schmid et al.

Continental rifts typically result from regional horizontal stretching of the lithosphere and in modelling studies, such rifts are typically assumed to be the result of orthogonal or oblique extension. However, in nature often V-shape rift geometries occur indicating an underlying rotational component that results in a divergence velocity gradient along plate boundaries. Consequently, the geometric, kinematic, and dynamic rift evolution in such rotational settings may significantly differ from those of orthogonal or oblique rifts. Here, we present new findings from an analogue modelling study using a crustal-scale model series with a rotational opening component to investigate the effect of such a rift-axis parallel divergence velocity gradient on fault growth and rift propagation towards the rotation axis.

We use a simplified two-layer system simulating an upper brittle and a lower ductile crust with an imposed initial mechanically weak zone on top of the viscous layer to ensure localized rifting. The experimental monitoring by means of a stereoscopic camera setup and X-Ray computed tomography (XRCT) enables a detailed and quantitative investigation of near-surface rift evolution and internal deformation, respectively. With the combination of 3D surface topography, 3D displacement fields, and XRCT, we gain a comprehensive understanding of deformation evolution in analogue models of rotational rifting. Our modelling results depict a novel characterization of normal fault growth under rotational extension and a rift evolution which is described by (1) rift propagation in two consecutive stages: A first stage showing bidirectional fault growth due to segment linkage with high rift propagation rates, and a second stage during which rift propagation occurs by unidirectional fault growth towards the rotation axis with linearly decreasing growth rates at decreasing distance to the rotation axis, (2) strain partitioning between competing conjugate normal faults with fault activity switching repeatedly from one segment of a normal fault to a segment on the oppositely dipping normal fault, and (3) active faulting migrating from the rift boundary faults inwards to intra-rift normal faults.

Our quantitative, spatiotemporal fault growth analysis reveals a characteristic segmentation of all deformation features listed above. The conclusion that the gradual decrease of the divergence velocity towards the rotation axis causes segmented deformation propagation is key and can help to understand natural examples of rotational rift settings such as the Taupo Rift Zone in New Zealand.

How to cite: Schmid, T., Schreurs, G., and Adam, J.: Fault growth and rift propagation during rotational continental rifting: Insights from an analogue modelling study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1970, https://doi.org/10.5194/egusphere-egu22-1970, 2022.

15:52–15:53
Questions - 1 min

15:53–15:58
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EGU22-8331
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ECS
Utomi Izediunor et al.

 As normal faults accumulate displacement, smearing of weaker fine-grained materials, such as clays, along their fault plane can reduce fault permeability and thus affect fluid flow in subsurface reservoirs, making clay smear development relevant for groundwater, geothermal and CO2 storage applications. Here we use analogue experiments to investigate the potential of smearing of weaker layers along fault planes in a multi-layer sequence of granular materials.  

The natural prototype is the interbedded limestone and marl sedimentary units of the Malm formation in a quarry in southern Germany. The normal faults in the quarry have small offset (usually < 50 cm) and dip between 40° – 65° predominantly trending NE – SW. We observe discontinuous marl smearing along the fault planes, which are surrounded by deformation zones with a dense tensile fracture population. Average limestone and marl bed thicknesses on both footwall and hanging wall is 32 cm and 4.5 cm, and 33 cm and 2.5 cm respectively.

Our analogue experiments are scaled to represent layers at quarry scale. We tested several sand and gypsum plaster mixtures using empirical and ring shear methods to find cohesive strength contrasts suitable for simulating the limestone-marl sequences. The material tests show that with increasing plaster content and confining pressure, cohesion increases, while the angle of internal friction shows a non-linear behaviour for plaster/sand mixtures. We here use sand for marl layers and gypsum for limestone. We sieve the materials in a 50 x 30 cm box of which half the base plate can drop down along a prescribed angle. We analyse deformation from 2D-timelapse and 3D-CT image data, using PIV and image analysis.

Models with sand (marl) layers within gypsum (limestone) without overburden show numerous mode I fractures at the free surface with localized fault planes. Shear zones are steep with dip angles in the range of 66° - 84°. Models with overburden form shear zones with dips ranging from 65° - 83°, forming less mode I fractures, but instead mainly shear fractures that cut across each cohesive layer. Sand smearing is observed to vary in models without overburden, while it is a consistent component of the fault zones at depth in models with overburden. We find that the quantity of sand smear is a function of the thickness of the embedded sand layers. The sand pours into large openings formed between cohesive gypsum powders with simultaneous mixing of the materials during fault displacement. This process causes an accumulation of sheared granular materials along the fault zone and in turn expands the shear zone width.

The experiments with overburden show steep dipping fragmented fault zones, as well as the formation of tensile fractures that form in, and cut through cohesive beds, similar to what is observed in the quarry. Sand smearing processes of rolling and mixing in dilatant portions during displacement is however more brittle in nature than ductile smearing observed in the quarry.

How to cite: Izediunor, U., Buiter, S., and Schmatz, J.: Analogue experiments of normal fault formation in multi-layers of alternating strength, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8331, https://doi.org/10.5194/egusphere-egu22-8331, 2022.

15:58–15:59
Questions - 1 min

15:59–16:04
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EGU22-6358
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ECS
Frank Zwaan and Guido Schreurs

When simulating lithosphere-scale rifting processes, analogue modellers have their model lithosphere float on top of a dense fluid representing the sub-lithospheric mantle (i.e. the asthenosphere). Such models provide crucial insights into rift evolution, but monitoring model-internal deformation has always been a major challenge. Here we present the results of new rifting experiments performed with a novel lithospheric-scale modelling machine that allows for X-ray CT-scanner, uniquely revealing the models’ internal evolution.

Our models involve a 4-layer lithosphere, with brittle layers for the competent upper crust and upper lithospheric mantel, and viscous layers for the ductile lower crust and lower lithospheric mantle. This model lithosphere is placed in a basin of glucose syrup simulating the asthenosphere and contained by mobile sidewalls. When stretching the model by moving these sidewalls apart (inducing either orthogonal or oblique extension), deformation is accompanied by syrup flow and isostatic compensation. A weakness within the upper mantle serves to localize deformation along the central axis of the model. We use photogrammetry and PIV techniques for detailed analysis of surface deformation, whereas CT imagery and PIV analysis of CT-sections provide unprecedented insights into internal model evolution.

We find that early on in orthogonal extension models, deformation initiates along the weakness in the upper mantle layer. This deformation is then transferred into the upper crust via shear zones in the lower crust, generating a dual graben structure there. In parts of the model, one of the grabens can become dominant and as extension progresses, so that a large shear zone cutting through the whole lithosphere forms (asymmetric, simple-shear rifting). In other parts of the model deformation may be more distributed so that both grabens are well-developed (symmetric, pure shear rifting). Meanwhile, the on-going stretching and thinning of the lithosphere splits the upper mantle layer, and the simulated lower mantle (and especially the asthenosphere) rises towards the model surface, bringing the lower mantle layer in contact with the lower crustal layer (i.e. necking of the lithosphere).

In oblique extension models initial deformation also localizes in the upper mantle layer, but no clear surface structures develops (except for a broad topographic depression along the central model axis). By increasing the extension velocity and thus the coupling between the upper mantle and upper crust, faulting initiated in the upper crust, creating two bands of en echelon grabens. Also in these models, we observe lithospheric necking.

Our (final stage) model results are similar to previous works. Yet the new CT-imagery provides the first-ever direct insights (both qualitative and quantitative) into the internal evolution of lithospheric-scale rift models. Furthermore, this new and versatile modelling machine in combination with our CT-scanning abilities provides a broad range of opportunities for advanced future lithospheric-scale modelling studies.

 

 

Figure: 3D CT image of an oblique extension model. UC: upper crust, LC: Lower crust, ULM: upper lithospheric mantle, LLM: lower lithospheric mantle, As: asthenosphere

 

How to cite: Zwaan, F. and Schreurs, G.: Lithospheric-scale experiments of continental rifting monitored in an X-Ray CT scanner, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6358, https://doi.org/10.5194/egusphere-egu22-6358, 2022.

16:04–16:05
Questions - 1 min

16:05–16:10
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EGU22-2743
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ECS
Daniele Maestrelli et al.

Continental break-up at Rift-Rift-Rift triple junctions commonly represents the “prequel” of oceanic basin formation. Currently, the only directly observable example of a Rift-Rift-Rift setting is the Afar triple junction where the African, Arabian and Somalian plates interact to form three rift branches, two of which are experiencing oceanization (the Gulf of Aden and the Red Sea). The younger of the three (the Main Ethiopian Rift) is still undergoing continental extension. We performed analogue and numerical models simulating continental rifting in a Rift-Rift-Rift triple junction setting to investigate the resulting structural pattern and evolution. By adopting a parametrical approach, we modified the ratio between plate velocities, and we performed single-phase (all the three plates move) and two-phase models (with a first phase where only one plate moves and a second phase where all the three plates move). Additionally, the direction of extension was changed to induce orthogonal extension only in one of the three rift branches. Our single-phase models suggest that differential extension velocities in the rift branches determine the localization of the triple junction, which is located closer to the rift branch experiencing slower extension velocities. Furthermore, imposed velocities affect the distribution of deformation and the resulting pattern of faults. The effect of a faster plate is to favour the formation of structures trending orthogonal to dominant velocity vectors, while faults associated with the movement of the slower plates remain subordinate. In contrast, imposing similar velocities in all rift arms leads to the formation of a symmetric fault pattern at the triple junction, where the distribution of deformation is similar in the three rift branches. Two-phase models reveal high-angle faults interacting at the triple junction, confirming that differential extension velocities in the three rift branches strongly affect the fault pattern development and highlighting geometrical similarities with the Afar triple junction.

How to cite: Maestrelli, D., Corti, G., Brune, S., Keir, D., and Sani, F.: Investigating Rift-Rift-Rift triple junctions through analogue and numerical modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2743, https://doi.org/10.5194/egusphere-egu22-2743, 2022.

16:10–16:11
Questions - 1 min

16:11–16:16
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EGU22-2847
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ECS
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Mingqi Liu et al.

Large offset detachment faults form with exhuming mantle-derived rocks into the seafloor at the slow and ultralow spreading ridges. However, their formation mechanism still remains partly elusive.  The thick axial lithosphere of ultraslow spreading ridges detected by seismic studies may prevent the formation of detachment faults. Previous studies have proposed that only the combination of both serpentinization and grain size reduction in the mantle lithosphere can result in detachment faults which are consistent with the natural cases. Here, through 3D self-consistent magmatic-thermomechanical numerical models with both brittle/plastic strain weakening and grain size evolution, we systematically investigate effects of these coupled brittle-ductile weakening processes on the formation of detachment faults at ultraslow spreading ridges. Numerical results show that ultraslow ridges spontaneously break into shorter and warmer magma-rich (10-20% of the ridge length) and longer and colder magma-starved segments (80-90% of the ridge length). Small grain size formed in the deep root of detachment faults near the brittle-ductile transition depth at the magma-starved amagmatic segments. Then with mantle rocks exhumation into the surface, the decreasing temperature leads to the growth of small grain size, consistent with the deformation process of detachment fault systems in the amagmatic segments of the eastern part of the Southwest Indian Ridge. Through quantitatively exploring effects of grain size reduction and strain weakening, we obtained that strain weakening may be the primary factor to control the formation of detachment faults at the ultra-slow spreading ridges, although grain size evolution can also influence the spreading pattern in case of small (<= 1 mm) initial grain size of the lithospheric mantle. Furthermore, we also found that the weak ductile domain induced by the very small initial grain size (<= 0.1 mm) promotes the formation of detachment faults in the models without grain size evolution.

How to cite: Liu, M., Rozel, A., and Gerya, T.: The effect of brittle-ductile weakening on the formation of detachment faults at ultraslow spreading ridges , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2847, https://doi.org/10.5194/egusphere-egu22-2847, 2022.

16:16–16:17
Questions - 1 min

16:17–16:22
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EGU22-5076
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ECS
Jaime Almeida et al.

Despite extensive research, intraplate deformation and associated earthquakes remain elusive. We argue that one potential reason for its occurrence is the interplay between the lithosphere and the upper mantle dynamic processes, specifically the lithosphere-asthenosphere interaction. To explore this possibility, we targeted the Gulf of Guinea and adjacent Western Africa, a region with low plate velocities and clear asthenosphere dynamics, which allows for the isolation of the underlying dynamic constraints which govern intraplate deformation. An in-depth understanding of intraplate deformation mechanisms will contribute towards the improvement of seismic hazard assessment away from plate boundaries.

Thus, here we present exploratory 3D numerical geodynamic models of the asthenosphere-lithosphere interaction in the Gulf of Guinea, ran with the state-of-the-art modelling code LaMEM. We employ different initial/boundary conditions such as: (a) different spreading rates for the Atlantic mid-ocean ridge (from 5 to 25 mm/yr), (b) rheological/lithological configurations (accounting for the cratonic/mobile nature of the region), (c) the presence/absence of weak zones (e.g., the Romanche/Central-African shear zones), and (d) the effect exerted by an active mantle plume. Seismicity data was employed to rank the models to ensure the validity of our results.

Preliminary results suggest that intraplate deformation within the Gulf of Guinea is influenced by the spreading rate of mid-ocean ridge, with stress being localized around the ocean-continent transition and existing shear zones.

This work was developed in the frame of SHAZAM (POCI-01-0415-FEDER-031475). FCT is further acknowledged for support through project UIDB/50019/2020-IDL.

How to cite: Almeida, J., Riel, N., Neres, M., Custódio, S., and Dumont, S.: Numerical modelling of lithosphere-asthenosphere interaction and intraplate deformation in the Gulf of Guinea , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5076, https://doi.org/10.5194/egusphere-egu22-5076, 2022.

16:22–16:23
Questions - 1 min

16:23–16:28
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EGU22-11034
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ECS
Anastasiia Tolstova et al.

The Mozambique Ridge is located in the southwestern Indian Ocean between
two Mesozoic ocean basins: the Natal Basin and the Mozambique Basin. The
Mozambique ridge is formed from several bathymetric plateaus rising to 3500 m from
the seabed. It is believed that the origin of the ridge is associated with its partial
separation from the outskirts of the African continent due to the activities of the Karoo
hotspot. Recent studies show that the northeastern part of the ridge is thinned
continental crust covered with sediments, and the southern part is characterized by a
large number of extrusion centers indicating increased igneous activity. Experimental
studies described in this work showed that the formation of the Mozambique ridge
occurred in the context of the destruction of the Afro-Antarctic continent with
structural heterogeneities in the lithosphere of the African continent and the influence
of the Karoo hotspot.
This work was supported by the Russian Science Foundation
(project no. № 22-27-00110).

How to cite: Tolstova, A., Dubinin, E., and Grokholsky, A.: Condition for the formation of the Mozambique ridge (physical modelling), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11034, https://doi.org/10.5194/egusphere-egu22-11034, 2022.

16:28–16:29
Questions - 1 min

16:29–16:34
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EGU22-9952
Lucia Perez Diaz

The South Atlantic played a key role in the formulation of plate tectonic theory, and plate modelling has come a long way since the very first computer-assisted reconstructions of this ocean basin in the 1960s. This basin remains an active area of exploration interest as well as an excellent case study to discuss the past, present and future of plate modelling and to reflect on the reasons why discrepancies still remain, decades later, between alternative models reconstructing its geological history.

Today, high-resolution studies featuring multiple closely spaced static reconstructions give the opportunity to determine plate motions and their changes through time in more detail than ever before. They act as the foundation stones for many modern-day interpretations and simulations, providing context for regional geological and tectonic studies, and constraints for predictions of past climates, depositional environments, the evolution of stress regimes and, ultimately, the location of natural resources. Defining accurate sets of rotations that describe plate motion, as well as quantifying the uncertainties in them, is thus increasingly important.

As well as becoming more sophisticated, modelling techniques have also somewhat diversified in recent years. This is well illustrated by the fact that, for any one region on the planet, it is relatively easy to find alternative (and often irreconcilable) plate reconstructions built either on the basis of different data, different methodologies, or both. This prompts the question “how does one choose the right plate model” (and is there even such a thing as the “right” plate model). Focusing on the South Atlantic basin and using recently released version 6.0 of the Neftex plate model, I will discuss how unlocking the next generation of plate models requires implementing a global approach anchored on the principles of geodynamics.

How to cite: Perez Diaz, L.: From deep time to the future: unlocking the next generation of plate models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9952, https://doi.org/10.5194/egusphere-egu22-9952, 2022.

16:34–16:35
Questions - 1 min

16:35–16:40
End of Block 1

Tue, 24 May, 17:00–18:30

Chairpersons: Valentina Magni, Michael Rudolf, Frank Zwaan

17:00–17:02
Introduction - Part 2

17:02–17:07
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EGU22-4212
Francesca Funiciello et al.

EPOS, the European Plate Observing System, is a unique e-infrastructure and collaborative environment for the solid earth science community in Europe and beyond (https://www.epos-eu.org/). A wide range of world-class experimental (analogue modelling and rock and melt physics) and analytical (paleomagnetic, geochemistry, microscopy) laboratory infrastructures are concerted in a “Thematic Core Service” (TCS) labelled “Multi-scale Laboratories” (MSL) (https://www.epos-eu.org/tcs/multi-scale-laboratories). Setting up mechanisms allowing for sharing metadata, data, and experimental facilities has been the main target achieved during the EPOS implementation phase. The TCS Multi-scale Laboratories offers coordination of the laboratories’ network, data services, and Trans-National access to laboratory facilities.

In the framework of data services, TCS Multi-Scale Laboratories promotes FAIR (Findable-Accessible-Interoperable-Re-Usable) (FAIR) sharing of experimental research data sets through Open Access data publications. Data sets are assigned with digital object identifiers (DOI) and are published under the CC BY license. Data publications are now conventionally citable in scientific journals and develop rapidly into a common bibliometric indicator and research metric. A dedicated metadata scheme (following international standards that are enriched with disciplinary controlled community vocabulary) facilitates ease exploration of the various data sets in a TCS catalogue (https://epos-msl.uu.nl/). Concerning analogue modelling, a growing number of data sets includes analogue material physical and mechanical properties and modelling results (raw data and processed products such as images, maps, graphs, animations, etc.) as well as software (for visualization, monitoring and analysis). The main geoscience data repository is currently GFZ Data Services, hosted at GFZ German Research Centre for Geosciences (https://dataservices.gfz-potsdam.de), but others are planned to be implemented within the next years.

In the framework of Trans-National access (TNA), TCS Multi-scale laboratories’ facilities are accessible to any researchers, creating new opportunities for synergy, collaboration and scientific innovation, according to TNAtrans-national access rules. TNA can be realized in the form of physical access (on-site experimenting and analysis), remote service (sample analysis) and virtual access (remotely operated processing). After three successful TNA calls, the pandemic has forced a moratorium on the TNA program.

The EPOS TCS Multiscale Laboratories framework is also providing the foundation for a comprehensive database of rock analogue materials, a dedicated bibliography, and facilitates the organization of community-wide activities (e.g., meetings, benchmarking) to stimulate collaboration among analogue laboratories and the exchange of know-how. Recent examples of these community efforts are also the contributions to the monthly MSL seminars, available on the MSL YouTube channel (https://www.youtube.com/channel/UCVNQFVql_TwcSBqgt3IR7mQ/featured), as well as the Special Issue on basin inversion in Solid Earth that is currently open for submissions  (https://www.solid-earth.net/articles_and_preprints/scheduled_sis.html#1160). 

How to cite: Funiciello, F., Rosenau, M., Dominguez, S., Willingshofer, E., ter Maat, G., Zwaan, F., Corbi, F., Eisermann, J. O., Guillaume, B., Souloumiac, P., Brizzi, S., Mastella, G., Reitano, R., Druguet, E., Schreurs, G., and Faccenna, C. and the EPOS Multi-Scale Laboratories Team: Sharing data and facilities in the analogue modelling community: the EPOS Multi-Scale Laboratories Thematic Core Service, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4212, https://doi.org/10.5194/egusphere-egu22-4212, 2022.

17:07–17:08
Questions - 1 min

17:08–17:13
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EGU22-767
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ECS
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Avinash Gupta and Ranjith Kunnath

We present a numerical scheme to study 3D fracture problems at a planar interface. This scheme is based on the spectral representation of the boundary integral equation method which involves the evaluation of elastodynamic convolutions at the interface. The advantage of this method is that it is numerically efficient as it calculates the field quantities only on the fracture plane rather than in the entire domain. In the current approach, spatial convolution is replaced by multiplication in the spectral domain which increase the computational efficiency. In the literature, Geubelle and Rice [1995] first introduced the 3D spectral representation of the formulation of Budiansky and Rice [1979]. In their approach, the time-convolution is performed of the displacement history at the interface. Later, 3D formulation for a bi-material interface was proposed by Breitenfeld and Geubelle [1998]. Recently, a spectral form of the Kostrov [1966] was proposed by Ranjith [2015] for 2D in-plane problems. In this approach, time-convolution is performed of the traction history at the interface. An advantage of this approach is that the convolution kernels for a bi-material interface can be expressed in closed form, whereas Breitenfeld and Geubelle [1998] had to obtain their convolution kernels numerically. In the present work, convolution kernels for 3D elastodynamic fracture problems at a bi-material interface are derived following the approach of Ranjith [2015].

How to cite: Gupta, A. and Kunnath, R.: Spectral formulation of the 3D elastodynamic boundary integral equations for a bi-material interface, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-767, https://doi.org/10.5194/egusphere-egu22-767, 2022.

17:13–17:14
Questions - 1 min

17:14–17:19
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EGU22-1670
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ECS
Michael Rudolf et al.

Inverted structures are some of the economically most important geological features worldwide. Besides their most common manifestation as traps for hydrocarbons, they are also interesting for the storage of CO2 and extraction of other resources such as heat, minerals or hydrogen. Analogue modelling is frequently used to understand the long-term geological evolution of basins and basin inversion as an addition to numerical and mathematical models. Most analogue models use granular materials, like sands and glass beads, to simulate the brittle-plastic rheology of the crust. The main driving mechanism for basin inversion, both in nature and analogue models is the reactivation of pre-existing structures. This is due to strain-dependent weakening which leads to a reduced strength of a fault or shear zone in comparison with the surrounding bulk material. If the structure comes to a rest, several mechanisms lead to a time-dependent restrengthening of the structure. Therefore, older structures are usually more resistant to reactivation than younger ones, in the same material. In this study we use an annular shear tester to quantify the healing of granular materials commonly used for analogue models. We take advantage of a large collection of analogue material samples at the Helmholtz Laboratory for Tectonic Modelling, coming from many laboratories worldwide. To estimate granular healing, we employ slide-hold-slide tests with hold times comparable to typical analogue models of basin inversion. We show that all materials tested exhibit healing which follows a power-law relation quantified by with a healing rate. For example, fused glass microbeads showed a healing rate of 0.025 per decade in hold time. This means that for a tenfold increase in hold time the strength required to reactivate the given fault increases by 2.5%. Consequently, if a fault is inactive for a longer period of time, it is slightly stronger in comparison with a fault with shorter inactivity. Comparing the healing exponent for several materials reveals that some materials show a stronger healing than others. Glass beads have a stronger healing than sands, with quartz sands having lower healing rates than garnet or feldspar sands. Geomechanical tests on natural materials (quartz and gypsum fault gouges) and measurements of seismic velocities across fault zones suggest that healing obeys a similar power law. The healing rates in real rocks are roughly equal or higher depending on the temperature and water saturation of the fault. Albeit small, this change in reactivation strength for analogue materials might have a strong influence on the structural style of inversion if the models are run with different timespans between extensional phase and compressional phase. With a typical range of experimental time-spans of a view seconds to several hours this may result in up to 10% difference in reactivation strength similar to the difference between static and dynamic friction. This becomes especially relevant, if the angles of the formed pre-existing structures are close to the angle of internal friction of the bulk material which is the default in models where reactivated structures have been formed self-consistently in a pre-inversion phase.

How to cite: Rudolf, M., Rosenau, M., and Oncken, O.: Influence of Time-dependent Healing on Reactivation of Granular Shear Zones in analogue models: A Community Benchmark, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1670, https://doi.org/10.5194/egusphere-egu22-1670, 2022.

17:19–17:20
Questions - 1 min

17:20–17:25
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EGU22-5879
Jun Liu et al.

The growth of faults is well studied with field methods, experiments and theoretical models. Fault evolution is largely established from a geometrical and kinematic point of view with respect to the growth of isolated faults and their mutual interaction. However, the dynamics of fault growth (e.g. stress shadowing, damage zone evolution, energy budgets) and the emergence of interactions over various spatial and temporal scales in larger fault networks is a topic of recent interest less illuminated so far. We here introduce a new experimental setup allowing to study “large-n” fault networks evolving in crustal-scale brittle and brittle-ductile analogue models. We document preliminary results helping to demonstrate and verify the capability of the approach.

The setup, called “The Expander”, builds on a traditional extensional setup with a basal rubber sheet expanded in one direction. The aspect ratio of the rubber sheet controls its lateral contraction (“Poisson’s effect”) and thus the bulk strain ratio under pure shear conditions. We can thus realize constrictional (prolate) to plane to flattening (oblate) kinematic basal boundary conditions depending on the sheet’s aspect ratio and whether we expand or relax the sheet. Evolving fault networks vary from anastomosing fold-and-thrust belts to conjugate sets of strike-slip fault networks to quasi-parallel normal fault populations, respectively. We apply digital image correlation (DIC) to track the kinematic surface evolution and photogrammetry (structure from motion, SFM) for topography evolution.

First observations suggest that strike-slip fault networks in a purely brittle crust under basal pure shear conditions evolve into compartments of synthetic faults, the size of which scale with brittle layer thickness similar to fault spacing. The scaling seems to be controlled by slip partitioned onto the individual faults and mediated by stress shadows. Numerical simulation of the experiment suggests that the compartmentalization might evolve further through sequential de-activation of smaller faults and collapse of deformation into a single regional scale master fault with or without prescribing a zone of crustal weakness (a “seed”). Further experiments are planned to test the fault pattern evolution for different mechanical stratigraphy (brittle-viscous layers, seeds) and kinematic boundary conditions.

How to cite: Liu, J., Rosenau, M., Brune, S., Kosari, E., Oncken, O., Rudolf, M., and Wrona, T.: The Expander: Growing fault networks under pure shear conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5879, https://doi.org/10.5194/egusphere-egu22-5879, 2022.

17:25–17:26
Questions - 1 min

17:26–17:31
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EGU22-10156
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ECS
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Luigi Massaro et al.

Dynamically scaled experiments allow the direct comparison of geometrical, kinematical and mechanical processes between model and nature. The geometrical scaling factor defines the model resolution, which depends mainly on the density and cohesive strength ratios of model material and natural rocks. Granular materials such as quartz sands are ideal for the simulation of upper crustal deformation processes as a result of similar nonlinear deformation behaviour of granular flow and brittle rock deformation. We compared the geometrical scaling factor of common analogue materials applied in tectonic models and identified a gap in model resolution corresponding to the outcrop and structural scale (1–100 m).

In this study, we present a new granular rock-analogue material (GRAM) with a dynamic scaling suitable for the simulation of fault and fracture processes in analogue experiments. The proposed material is composed of silica sand and hemihydrate powder and is suitable to form cohesive aggregates capable of deforming by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, GRAM is characterized by a similar stress-strain curve as dry silica sand, has a cohesive strength of 7.88 kPa and an average density of 1.36 g cm−3. The derived geometrical scaling factor is 1 cm in model = 10.65 m in nature. For a large-scale test, GRAM material was applied in strike-slip analogue experiments. Early results demonstrate the potential of GRAM to simulate fault and fracture processes, and their interaction in fault zones and damage zones during different stages of fault evolution in dynamically scaled analogue experiments.

How to cite: Massaro, L., Adam, J., Jonade, E., and Yamada, Y.: New granular rock-analogue materials for simulation of multi-scale fault and fracture processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10156, https://doi.org/10.5194/egusphere-egu22-10156, 2022.

17:31–17:32
Questions - 1 min

17:32–17:37
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EGU22-9653
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ECS
Jasper Smits et al.

Since the 19th century pioneering work of Sir James Hall, physical analogue modelling has been proven a valuable method for the study of geological phenomena and has significantly contributed to understanding fundamental mechanisms of crust and lithosphere deformation. Traditionally, in such analogue scale models, structural deformation is monitored and quantified using top-view images or cross-sections, where the latter allow for portraying the final state of internal deformation of the model in great detail. Monitoring the evolution of internal deformation while the experiment is running is however a major challenge, and currently is possible only with X-ray scanning using medical-type CT scanners. These, however, put stringent limitations on size of the model and, thus, the possible geometric configurations related to different modelling setups.

To tackle these limitations, we are developing a novel method to image the evolving interior of analogue scale models using ultrasonic techniques. Similar to reflection seismology used in field studies, the internal structure of the analogue model can be imaged using sound waves. We employ a completely non-contact and non-invasive method, utilizing a laser Doppler vibrometer to detect the arrivals of seismic body waves at the model surface. A laser pulse from a powerful pulsed laser acts as a point source and is used to introduce acoustic waves in the model. By moving the detector and source, acoustic data is recorded for a number of source-recorder combinations, allowing the reconstruction of the internal layering and structure along cross sections, as will be illustrated by the results of several tests with analogue models and other samples. By developing this technique, we provide novel tools to characterize the acoustic behaviour of subsurface structures under well-controlled laboratory conditions with the aim of improving our understanding of waveforms and wave propagation in analogue models and earth materials in general.

How to cite: Smits, J., Beekman, F., Vasconcelos, I., Willingshofer, E., Van Wijk, K., and Matenco, L.: Ultrasonic imaging of analogue scale models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9653, https://doi.org/10.5194/egusphere-egu22-9653, 2022.

17:37–17:38
Questions - 1 min

17:38–17:43
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EGU22-7776
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ECS
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Highlight
Adriano Gualandi et al.

Earthquakes are a complex natural phenomenon. They typically are the result of frictional instabilities along preexisting weakness zones called faults. The strain slowly builds up in the fragile Earth crust because of the presence of an external loading counterbalanced by friction forces at the faults’ interface. When the load cannot be balanced by the friction any further, the fault slips releasing the accumulated strain. Friction is a nonlinear phenomenon, and as such frictionally controlled systems may be subject to chaotic behavior. Seismic cycle analogs can be reproduced with rock friction experiments in the laboratory with a double direct shear apparatus. We show that laboratory earthquakes follow a low-dimensional random attractor. We explain the observations with a model of stochastic differential equations based on the rate- and state-friction framework. We show that small perturbations (less than 1‰) on the shear and normal stress can induce laboratory earthquakes aperiodic behavior with coefficient of variations of the order of some percent. The nonlinear nature of friction amplifies small scale perturbations, making mid-long term predictions of the system possible only statistically even for stick-slip events in a well controlled environment like the laboratory.

How to cite: Gualandi, A., Faranda, D., Marone, C., and Mengaldo, G.: Stochastic Chaos in Laboratory Earthquakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7776, https://doi.org/10.5194/egusphere-egu22-7776, 2022.

17:43–17:44
Questions - 1 min

17:44–17:49
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EGU22-12635
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ECS
Carlos R. Nogueira and Fernando O. Marques

17:49–17:50
Questions - 1 min

17:50–17:55
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EGU22-3265
Michele Cooke et al.

Crustal deformation occurs both as localized slip along faults and distributed deformation off faults; however, we have few robust geologic estimates of off-fault deformation over multiple earthquake cycles. Scaled physical experiments simulate crustal strike-slip faulting and allow direct measurement of the ratio of fault slip to regional deformation, quantified as Kinematic Efficiency (KE). We offer an approach for KE prediction using a 2D Convolutional Neural Network (CNN) trained directly on images of fault maps produced by physical experiments of strike-slip loading of wet kaolin. A suite of experiments with different loading rate and basal boundary conditions, contribute over 13,000 fault maps throughout strike-slip fault evolution. Strain maps allow us to directly calculate KE and its uncertainty, utilized in the loss function and performance metric. The trained CNN achieves 91% accuracy in KE prediction of an unseen dataset. We then apply this CNN trained on wet kaolin experiments to strike-slip experiments in dry sand. The different rheology of sand and kaolin may lead to different relationships between fault geometry and off-fault deformation, which can be detected by differences in the predictive power of the CNN trained only on kaolin.  We also apply the trained CNN to crustal maps of off-fault deformation over coseismic, 10ka and 1 Ma time scales. The CNN predicted off-fault deformation overlap available geologic estimates.

How to cite: Cooke, M., Elston, H., Chaipornkaew, L., Visage, S., Souloumniac, P., and Mukerji, T.: Prediction of Off-Fault Deformation from Strike-slip Fault Structures in clay and sand experiments using Convolutional Neural Networks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3265, https://doi.org/10.5194/egusphere-egu22-3265, 2022.

17:55–17:56
Questions - 1 min

17:56–18:01
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EGU22-8822
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ECS
Jana Schierjott et al.

Transform faults and non-transform offsets define the bounds of mid-ocean ridge spreading segments, but tectonic and magmatic controls on the length of segments and the morphology of intervening offsets are poorly understood. A general observation at intermediate and slow-spreading oceanic environments is that localized strike-slip motion along transform faults tends to occur on larger offsets in space or crustal age, whereas more diffuse deformation at non-transform zones occurs at shorter offsets distances. In addition, variables such as lithospheric thickness, the size and spacing of faults, and the fraction (M) of extension accommodated by magmatic accretion (rather than faulting) are known to influence the overall morphology of the ridge segment and its vicinity. We hypothesize that the decrease in the amount of magmatic extension along the ridge segment towards the discontinuity along with the ridge segment offset play a role in defining the transition between transform and non-transform offsets.

In this study, we employ a 3D-numerical model to investigate how the relative amounts of fault- or magma-accommodated spreading and distance offset (D) between ridge segments control the development of transform versus non-transform offsets. Our model employs a ridge-like initial temperature structure, with magma intrusion simulated by adding a divergence to the right-hand-side of the continuity equation within a magmatic accretion zone at the ridge axis. M, the fraction of magmatically compensated spreading inside the magmatic accretion zone, can be varied along strike. By using a visco-elasto-plastic formulation the model can simulate the spontaneous formation and evolution of normal faults that accommodate part of the spreading. The temperature field is allowed to evolve and the model accounts for an increased, temperature-dependent conductivity around each ridge segment. We vary both the offset distance D separating two axes of magmatic accretion as well as the length L over which M decreases along the ridge axes towards the discontinuity. We find that increasing L leads to non-transform offsets, particularly for small offset distances D. As D increases, the occurrence of the offset zone is less prominently dominated by L. Depending on M, the style of faulting differs along the magmatic segments. While for M>0.5 we observe migrating faults creating topography similar to abyssal hills, values for M that are smaller or equal to 0.5 lead to stationary faults which are located closer to the ridge axis. 

How to cite: Schierjott, J., Ito, G., Behn, M., Morrow, T., Tian, X., and Kaus, B.: Transform versus non-transform offsets controlled by offset length and the variation in magmatic accretion within the offset zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8822, https://doi.org/10.5194/egusphere-egu22-8822, 2022.

18:01–18:02
Questions - 1 min

18:02–18:07
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EGU22-1058
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ECS
Wengang He

The diapir structure is closely related to the distribution of oil and gas resources and has received extensive attention. In this regard, previous works have conducted much research on it. So far, many important achievements and understandings have been obtained on the formation environment and deformation styles of diapir structures, but there are few studies on the formation mechanism of salt or mud diapir initiation and its downbuilding. This study uses analog modeling to establish four sets of combined models of the basal silicon layer and overlying quartz sand, including the differences in initial geomorphology, the thickness of the covering layer above the ductile layer, sedimentary rate, and basal and lateral friction. Results show that the difference in geomorphology is the initial necessary condition for the formation of salt dome or mud dome structure, i.e., the extension, compression environment, and weak zone formed by tectonic activity are all conducive to the rapid start of the diapir structure. The formation of diapir downbuilding, rapid deposition loading, thick initial covering layer above the ductile layer, and significant basal and lateral friction will inhibit the development of early diapirs. In contrast, slow deposition rate, thin initial covering layer above the ductile layer, and reduced basal and lateral friction will promote the growth of early diapirs. Simultaneously, in the middle and late stages of diapir downbuilding, diapirs will grow and deform rapidly with the loading of the deposition rate. Based on the physical modeling results and natural deformation of the diapiric structure, comprehensive analysis shows that diapir downbuilding results from the combined effects of geomorphology, deposition rate, formation temperature and pressure, and diapir fluid depth. It is found that the salt diapir downbuilding in the North Sea Basin and mud diapir downbuilding in the Andaman back-arc basin are similar to the formation mechanism of analog modeling downbuilding in this paper.

 

Keywords: Diapir Structure; Downbuilding; Initial Geomorphology; Sedimentary Rate; Covering Thickness; Basal and Lateral Friction; Analogue Modeling

How to cite: He, W.: Diapiric initiation and formation mechanism of diapir’s downbuilding—Insights from analogue modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1058, https://doi.org/10.5194/egusphere-egu22-1058, 2022.

18:07–18:08
Questions - 1 min

18:08–18:13
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EGU22-10849
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ECS
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Highlight
Nadezda Chertkova et al.

Primary inclusions in natural diamonds provide unique information about deep-seated mantle minerals and fluids. Findings of the VI and VII modifications of H2O-ice as inclusions in diamonds show the presence of aqueous fluids at different depths in the diamond-bearing mantle (Kagi et al., 2000; Tschauner et al., 2018). In this work, we apply various experimental techniques for the investigation of mineral associations and H2O phases, captured as inclusions in diamonds, in the pressure range from 4 to 8 GPa and at temperatures from 500 °C to 1250 °C. In situ observations using diamond anvil cell (DAC) technique revealed crystallization of ice VII in association with ilmenite and olivine minerals upon cooling from 890 °C at 4 GPa, in agreement with the data, obtained from natural samples by Tschauner et al. (2018). Heating of this assemblage to 1200 °C at 6 GPa results in the formation of another mineral association, which includes ilmenite, pyroxene and clinohumite. Obtained experimental results can be used to reconstruct the pressure and temperature conditions of mineral and fluid inclusions capturing upon diamond growth and transfer in the lithosphere.  

This work was supported by grant No. 20-77-00079 from the Russian Science Foundation.

How to cite: Chertkova, N., Spivak, A., Burova, A., Zakharchenko, E., Litvin, Y., Safonov, O., and Bobrov, A.: Experimental study on the conditions of inclusions capturing during diamond growth in the upper mantle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10849, https://doi.org/10.5194/egusphere-egu22-10849, 2022.

18:13–18:14
Questions - 1 min

18:14–18:24
End of Block 2