Influence of uniform basement extension on faulting in cover sediments

Harper, T.R.; Fossen, Haakon; Hesthammer, Jonny

doi:10.1016/s0191-8141(00)00107-3

Cited by 13 publications

(5 citation statements)

References 14 publications

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“…Similarly, numerical modelling using kinematic, ¢nite-element and discrete-element approaches has also proven successful in investigating faulting and associated folding (e.g. Erslev, 1991;Saltzer & Pollard, 1992;Hardy & McClay, 1999;Harper et al, 2001;Allmendinger & Shaw, 2000;Johnson & Johnson, 2002a, b;Finch et al, 2003). Although these numerical models have highlighted some of the important controls on fault-propagation folding, one key drawback is that, with the exception of discrete-element models, they prescribe the rate at which the basement fault propagates into the cover, not allowing investigation of the e¡ect of varying mechanics within the overlying cover on rates and styles of fault propagation and associated folding.…”

Section: Introductionmentioning

confidence: 99%

Discrete‐element modelling of extensional fault‐propagation folding above rigid basement fault blocks

2004

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We employed a discrete‐element technique to investigate the effects of cover strength and fault dip on the style of fault‐propagation folding above a blind normal fault. Deformation in the cover is initially characterised by an upward‐widening monocline that is often replaced, with continued slip on the basement fault, by a single, through‐going fault. Localisation on a single fault produces hangingwall synclines and footwall anticlines as a result of breaching of the earlier monocline and which do not represent ‘drag’ against the fault. As basement fault dip decreases the width of the monocline at the surface increases. Experiments varying the strength of the overburden material illustrate the control that cover strength has on both fault propagation and folding in the cover. Reduction of the strength of the cover results in: (1) the width of the monocline above the fault tip increasing, and (2) more marked footwall thinning and hangingwall thickening of beds. In contrast, an increase in cover strength results in a narrower monocline and rapid propagation of the basement fault into the cover. In multi‐layer (variable strength) experiments simultaneous faulting of competent layers and flow of weaker layers produces complex structural relationships. Faults in the cover die out up and down section and do not link to the basement fault at depth. Similarly, complex macroscopically ductile characteristics such as footwall thinning and hangingwall thickening can be juxtaposed against simple brittle fault cut‐offs. These relationships must be borne in mind when interpreting the field and seismic expression of such structures. We discuss the modelling results in terms of their implications for structural interpretation and the surficial expression of fault‐related folding in extensional settings.

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Section: Introductionmentioning

confidence: 99%

Discrete‐element modelling of extensional fault‐propagation folding above rigid basement fault blocks

2004

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“…The effect of varying the basal boundary condition on fault geometry was studied by Harper et al [2001], but its effect on fault size scaling is unknown. The experiments presented in Figure 4 all feature a deforming layer lying above an inviscid fluid, giving a local isostatic boundary condition at the base of the model.…”

Section: Resultsmentioning

confidence: 99%

Controls on strain localization in a two‐dimensional elastoplastic layer: Insights into size‐frequency scaling of extensional fault populations

Hardacre

Cowie

2003

J. Geophys. Res.

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[1] We use a two-dimensional (2-D) finite element code to investigate how mechanical properties and boundary conditions influence progressive strain localization during extension of a 2-D elastoplastic layer. The deforming medium is modeled using a strain softening Von Mises rheology, with a Gaussian heterogeneity in yield strength distributed randomly in space. Specifically, we examine the effects of changing (1) the thickness of the deforming layer, (2) the basal boundary condition, (3) the range of strengths in the deforming layer, (4) the strength loss on failure, and (5) the total accommodated strain. Discrete zones of plastic shear strain are observed to nucleate and grow progressively during each experiment. In order to quantify and thus discriminate between the deformation patterns produced under differing conditions, we calculate the size-frequency distributions of the shear band populations. Size is defined as the total plastic strain represented by each discrete structure. A wide range of size-frequency distributions is observed, including both power law and exponential as well as distributions that show breaks in scaling with a transition from power law (at small sizes) to exponential (at large sizes). We show that these variations in population statistics are directly reflecting a change in strain localization in space and time caused by changing model parameters. Furthermore, by making an analogy between the model shear bands and tectonic faults, we provide insights into key features of fault size-frequency distributions that have been measured in continental and oceanic extensional settings and also observed in analogue experiments.INDEX TERMS: 8015 Structural Geology: Local crustal structure; 8020 Structural Geology: Mechanics; 8010 Structural Geology: Fractures and faults; 8109 Tectonophysics: Continental tectonics-extensional (0905); 8159 Tectonophysics: Rheology-crust and lithosphere; KEYWORDS: faulting, localization, scaling, extension, modeling Citation: Hardacre, K. M., and P. A. Cowie, Controls on strain localization in a two-dimensional elastoplastic layer: Insights into size-frequency scaling of extensional fault populations,

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“…Results of geological experiments [38,52] suggest that special attention has to be paid in order to achieve a uniform strain distribution inside the rubber membrane. Due to this inference and with respect to a good reproducibility of the experiments, a special mechanism has been designed that provides a constant displacement gradient inside the rubber membrane during any state of the experiment.…”

Section: Experimental Devicementioning

confidence: 99%

Centrifuge model tests on sand specimen under extensional load

Wolf

König

Triantafyllidis

2004

Int. J. Numer. Anal. Meth. Geomech.

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SUMMARYThe appearance of shear banding in granular materials has been investigated intensively during the last decades and is still of ongoing importance in terms of understanding the stress-strain behaviour of the material, the localization phenomena and the interaction between soil and structure. Only less attention has been paid to the occurrence of systems of shear bands although such systems can be identified in geotechnical structures as well as in geological formations. In this paper we present results of experiments on sand specimens under extensional load in natural gravity as well as in increased gravity in the centrifuge where the influence of the stress level on the geometry of a shear band pattern, specified by the spacing of the shear bands and the angle between failure surfaces and minor stress direction, has been investigated. Xray technique has been used to visualize the failure zones inside the specimen, an optical measurement system called Digital Image Correlation has been applied to identify and observe the appearing deformation mechanism on the sides of the specimens in natural gravity as well as during the flight in the centrifuge. It can be shown that the geometry of the shear band pattern is sparsely influenced by the change of the stress level.

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Influence of uniform basement extension on faulting in cover sediments

Cited by 13 publications

References 14 publications

Discrete‐element modelling of extensional fault‐propagation folding above rigid basement fault blocks

Discrete‐element modelling of extensional fault‐propagation folding above rigid basement fault blocks

Controls on strain localization in a two‐dimensional elastoplastic layer: Insights into size‐frequency scaling of extensional fault populations

Centrifuge model tests on sand specimen under extensional load

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