The internal structure of fault zones in basaltic sequences

Holland, Marc; Urai, János L.; Martel, Stephen J.

doi:10.1016/j.epsl.2006.05.035

Cited by 86 publications

(108 citation statements)

References 32 publications

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“…deformed cohesive basalts on the Big Island of Hawaii show similar structures and suggest that the dilatant segments of faults connect to a single (non dilatant) fault at depth, and that larger, unobserved cavities are located below rotated blocks [12].…”

Section: Introductionmentioning

confidence: 82%

“…However, in the numerical models, this angle can be varied [18][19] down by a motor, with a constant velocity, two side tables are pushed symmetrically to the sides, forming a master graben. The maximum horizontal elongation is 11% (see also [12,16] for more details).…”

Section: Analogue Modelmentioning

confidence: 99%

“…The set-up chosen in all models is a graben bounded by normal faults with a dip of 60° [12,16]. However, in the numerical models, this angle can be varied [18][19] down by a motor, with a constant velocity, two side tables are pushed symmetrically to the sides, forming a master graben.…”

Section: Analogue Modelmentioning

confidence: 99%

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The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

Gent

Abe

Urai

et al. 2010

EPJ Web of Conferences

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Abstract. We compare analogue and numerical models of dilatational fractures at low confining stress. These structures form an effective conduit for fluid flow in the field, but are difficult to model since they form in cohesive materials at low stresses. We use a truly cohesive powder for the analogue models and a Discrete Element Model (DEM) with brittle-elastic bonds for the numerical modelling. We show that despite variations in the model type, small differences in the location of initial fractures and the way these structures link-up to control the evolution of the model, the observed structures are robust. Three structural zones develop where different fault types dominate. In 3D numerical models we show an increase of the porosity on the fault zone with increasing deformation. The progradation direction is shown to be controlled by the position of the fracture. The combination of analogue models with cohesive powder and DEMs with internal cohesion is an excellent tool to study the evolution of open fractures.

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Section: Introductionmentioning

confidence: 82%

Section: Analogue Modelmentioning

confidence: 99%

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The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

Gent

Abe

Urai

et al. 2010

EPJ Web of Conferences

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“…The mechanical properties of the cohesive hemihydrate powder were tested extensively by van Gent et al (2010) and used in several experimental studies (Holland et al, 2006(Holland et al, , 2011Kettermann et al, 2016). After sieving, the powder tends to form clusters with sizes of 10-400 µm.…”

Section: Methodsmentioning

confidence: 99%

“…The set-up consists of a mechanically layered model deforming above a rigid basement fault. We used sand to simulate the sandstones of the Permian and Carboniferous, and cohesive hemihydrate powder (Holland et al, 2006(Holland et al, , 2011van Gent et al, 2010;Kettermann et al, 2016) to simulate the Zechstein anhydrites and carbonates (Fig. 4).…”

Section: Physical Modelsmentioning

confidence: 99%

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

Kettermann

Abe

Raith

et al. 2017

Netherlands Journal of Geosciences

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The presence of salt in dilatant normal faults may have a strong influence on fault mechanics in the Groningen field and on the related induced seismicity. At present, little is known of the structure of these fault zones. This study starts with the geological evolution of the Groningen area, where, during tectonic faulting, rock salt may have migrated downwards into dilatant faults. These fault zones therefore may contain inclusions of rock salt. Because of its rate-dependent mechanical properties, the presence of salt in a fault may introduce a loading-rate dependency into fault movement and affect the distribution of magnitudes of seismic events. We present a first-look study showing how these processes can be investigated using a combination of analogue and numerical modelling. Full scaling of the models and quantification of implications for induced seismicity in Groningen require further, more detailed studies: an understanding of fault zone structure in the Groningen field is required for improved predictions of induced seismicity. The analogue experiments are based on a simplified stratigraphy of the Groningen area, where it is generally thought that most of the Rotliegend faulting has taken place in the Jurassic, after deposition of the Zechstein. This suggests that, at the time of faulting, the sulphates were already transformed into brittle anhydrite. If these layers were sufficiently brittle to fault in a dilatant fashion, rock salt was able to flow downwards into the dilatant fractures. To test this hypothesis, we use sandbox experiments where we combine cohesive powder as analogue for brittle anhydrites and carbonates with viscous salt analogues to explore the developing fault geometry and the resulting distribution of salt in the faults. Using the observations from analogue models as input, numerical models investigate the stick-slip behaviour of fault zones containing ductile material qualitatively with the discrete element method (DEM). Results show that the DEM approach is suitable for modelling the seismicity of faults containing salt. The stick-slip motion of the fault becomes dependent on shear loading rate with a modification of the frequency-magnitude distribution of the generated seismic events.

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Dike‐induced contraction along oceanic and continental divergent plate boundaries

Trippanera

Acocella

Ruch

2014

Geophysical Research Letters

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The axis of divergent plate boundaries shows extension fractures and normal faults at the surface. Here we present evidence of contraction along the axis of the oceanic ridge of Iceland and the continental Main Ethiopian Rift. Contraction is found at the base of the tilted hanging wall of dilational normal faults, balancing part of their extension. Our experiments suggest that these structures result from dike emplacement. Multiple dike injection induces subsidence above and uplift to the sides of the dikes; the transition in between is accommodated by reverse faults and subsequent peripheral inward dipping normal faults. Our results suggest that contraction is a direct product of magma emplacement along divergent plate boundaries, at various scales, marking a precise evolutionary stage and initiating part of the extensional structures (extension fractures and normal faults).

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The internal structure of fault zones in basaltic sequences

Cited by 86 publications

References 32 publications

The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

Dike‐induced contraction along oceanic and continental divergent plate boundaries

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