The Experts below are selected from a list of 19938 Experts worldwide ranked by ideXlab platform
Stuart Hardy - One of the best experts on this subject based on the ideXlab platform.
-
Discrete element modelling of extensional, growth, Fault-Propagation folds
Basin Research, 2019Co-Authors: Stuart HardyAbstract:Abstract Extensional Fault‐Propagation folds are now recognised as being an important part of basin structure and development. They have a very distinctive expression, often presenting an upward‐widening monocline, which is subsequently breached by an underlying, propagating Fault. Growth strata, if present, are thought to provide a crucial insight into the manner in which such structures grow in space and time. However, interpreting their stratigraphic signal is neither straightforward nor unique. Both analogue and numerical models can provide some insight into fold growth. In particular, the trishear kinematic model has been widely adopted to explain many aspects of the evolution and geometry of such Fault‐Propagation folds. However, in some cases the materials/rheologies used to represent the cover do not reproduce the key geometric/stratigraphic features of such folds seen in nature. This appears to arise from such studies not addressing adequately the very heterogenous mechanical stratigraphy seen in many sedimentary covers. In particular, flexural slip between beds/layers is often not explicitly modelled but, paradoxically, it appears to be an important deformation mechanism operative in such settings. Here, I present a 2D discrete element model of extensional Fault‐Propagation folding which explicitly includes flexural slip between predefined sedimentary units or layers in the cover. The model also includes growth strata and shows how they may reflect the various evolutionary stages of fold and Fault growth. When flexural slip is included in the modelling scheme, the resultant breached monoclines and their growth strata are strikingly similar to some of those seen in nature. Results are also compared with those obtained using simple, homogeneous, frictional‐cohesive and elastic cover materials. Both un‐lithified and lithified growth strata are considered and clearly show that, rather than just being passive recorders of structural evolution, growth strata can themselves have an important effect on Fault‐related fold growth. Implications for the evolution of and strain within, the resultant growth structures are discussed. A final focus of this study is the relationship that trishear might have with the upward‐widening zone of flexural slip activation away from a Fault tip singularity.
-
Discrete element modelling of the influence of cover strength on basement-involved Fault-Propagation folding
Tectonophysics, 2006Co-Authors: Stuart Hardy, Emma FinchAbstract:Abstract A discrete element model is used to investigate the influence of sedimentary cover strength on the development of basement-involved Fault-Propagation folds. We find that uniformly weak cover best promotes the development of classical, trishear-like Fault-related folds showing marked anticlinal thinning and synclinal thickening, with cover dips increasing downwards towards the Fault tip. Uniformly strong cover results in more rounded fold forms with only minor hinge thickening/thinning and significant basement Fault-Propagation into the sedimentary cover. Heterogeneous, layered, cover sequences with marked differences in strength promote the development of more complex and variable fold forms, with a close juxtaposition of brittle and macroscopically ductile features, which diverge from the predictions of simple kinematic models. In these structures the upper layers are often poor indicators of deeper structure. In addition, we find that in layered cover sequences Fault-Propagation into the cover is a complex process and is strongly buffered by the weaker cover units.
-
Kinematic modelling of extensional Fault-Propagation folding
Journal of Structural Geology, 1999Co-Authors: Stuart Hardy, Ken McclayAbstract:Abstract Many studies have shown that in extensional basins discrete Faulting at depth is commonly linked to more distributed deformation, in particular folding, at higher levels. Such extensional Fault-Propagation folds are particularly common where there is a distinct mechanical contrast between Faulted basement and sedimentary cover. Outcrop and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation (monoclines) above discrete Faults at depth. With increasing displacement (strain) the folds are cut by Faults as they propagate upwards into the cover. To date, however, there has been little investigation into the kinematics of linked basement Faulting and extensional Fault-Propagation folding. Here we present a two-dimensional kinematic model of linked basement Faulting and Fault-Propagation folding which is based upon trishear. The model allows investigation of the influence of shear zone geometry and the rate of Fault Propagation upon the style of folds and the strains associated with them. The evolution of linked basement Faulting and folding predicted by the model is compared in detail to that observed in an analogue model. The kinematic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies.
-
Numerical modeling of trishear Fault Propagation folding
Tectonics, 1997Co-Authors: Stuart Hardy, Mary FordAbstract:In contrast to kink band migration modeling methods, trishear numerical models produce Fault Propagation folds with smooth profiles and rounded hinges. Modeled fold hinges tighten and converge downward, within a triangular zone of distributed deformation which is focused on the Fault tip. Such features have been reported from field studies and are also seen in analogue models of compressional deformation. However, apart from its initial application to Laramide folds, little quantitative work has been undertaken on trishear Fault Propagation folding in other settings. In addition, no study has been undertaken into the growth strata which might be associated with such structures. This paper uses an equivalent velocity description of the geometric model of trishear, together with models of erosion and sedimentation, to investigate trishear Fault Propagation folding of both pregrowth and growth strata. The trishear model is generalized to include a variety of Fault Propagation to slip ratios and Fault Propagation from a flat decollement. The models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata. When total slip on a structure is high, the model predicts overturned pregrowth and growth strata. During the initial stages of deformation, beds in the forelimb thicken but later thin when they become steep or overturned. The effect of variations in Fault Propagation to slip ratios on two‐dimensional finite strain in the models is assessed by the use of initially circular strain markers. High Fault Propagation to slip (p/s) ratios lead to narrow zones of high finite strain, while lower p/s ratios lead to more ductile deformation and broader zones of high strain. In all cases, hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating Fault. Modeled structures are compared with natural examples.
-
A velocity description of constant-thickness Fault-Propagation folding
Journal of Structural Geology, 1997Co-Authors: Stuart HardyAbstract:Abstract The expression of the geometric model of constant-thickness Fault-Propagation folding as a velocity description of deformation allows the derivation of rates of displacement, uplift and Fault Propagation. The velocity model of Fault-Propagation folding and sedimentation are combined in a finite-difference scheme, and two examples of growth strata associated with overturned fold forelimbs illustrate the application of the model.
Josep Poblet - One of the best experts on this subject based on the ideXlab platform.
-
Structural analysis and deformation architecture of a Fault-Propagation fold in the southern Cantabrian Mountains, NW Iberian Peninsula
Trabajos de Geologia, 2010Co-Authors: M. Masini, Mayte Bulnes, Josep PobletAbstract:Fault-Propagation folds are important contractional structures developed in upper crustalconditions. Here we analyze a Fault-Propagation fold, made up of Carboniferous limestones, sited inthe Cantabrian fold and thrust belt, NW Iberian Peninsula. The technique employed consists ofdetailed structural analysis integrated with cross-section restoration. Such approach allowed us to validatethe geological interpretation and to decipher the deformation architecture using an inverse modelbased on strain markers. The results are illustrated overlapping contour maps and diagrams on top ofthe deformed, present-day cross section.
-
Growth stratal architectures associated to decollement folds and Fault-Propagation folds. Inferences on fold kinematics
Tectonophysics, 1997Co-Authors: Fabrizio Storti, Josep PobletAbstract:Abstract In many thrust and fold belts, asymmetric folds with overturned or steeply dipping forelimbs and gently dipping backlimbs are commonly interpreted as thrust-related folds. Determining the folding mechanism exclusively from the final fold geometry in the pre-growth units is possible only for a limited suite of structures. The nature of fold-thrust interaction in shallow structures can be inferred by coupling the fold geometric analysis with the study of the syntectonic sediment stratal architectures. Several factors such as axial surface activity, fold uplift, limb rotation and limb widening rates, together with sedimentation and erosion rates, control growth strata patterns. Because the evolutionary path of most of these parameters depends on the folding kinematics, different growth stratal architectures are expected for different thrust-related anticlines. In this paper we examine the influence of the above factors on growth stratal geometries associated to a simple kink band, and then we apply the same approach to kinematic models of decollement folding and Fault-Propagation folding. Four geometric approaches are used to account for the geometry and kinematics of anticlines located at the tip of a blind thrust: Fault-Propagation folding with no excess layer-parallel shear, Fault-Propagation folding with progressive layer-parallel shear, constant limb length decollement folding and variable limb length decollement folding. Whereas Fault-Propagation folding with no excess layer-parallel shear is a self-similar folding mechanism, the other three types involve limb rotation. Coherent geometries between growth and pre-growth sequences develop at high sedimentation rates in the crest of Fault-Propagation folds, and incoherent ones in decollement folds. Minor differences within growth strata patterns occur at low sedimentation rates, and when erosion affects the crest of the anticlines.
-
The velocity description of deformation. paper 2: sediment geometries associated with Fault-bend and Fault-Propagation folds
Marine and Petroleum Geology, 1995Co-Authors: Stuart Hardy, Josep PobletAbstract:Abstract A general tectono-sedimentary forward modelling equation is used to derive two-dimensional numerical models of sediment geometries associated with developing Fault-bend and Fault-Propagation folds. These styles of folding are described in terms of velocity models of deformation and are linked with syn-tectonic erosion, transport and sedimentation. The resultant two-dimensional numerical models simulate pre-growth and growth strata in both submarine and subaerial settings. The geometries and relationships produced by the models are broadly similar to those seen in natural examples. However, complex stratal geometries may be generated which are significantly different to those produced by previous models. Growth strata associated with Fault-bend and Fault-Propagation folds are also compared and the distinguishing features of each mode of folding discussed. The forward models presented in this paper have predictive capabilities in terms of possible sediment geometries associated with Fault-bend and Fault-Propagation folds and also in terms of the amount of deformation or erosion that a part of a structure may have undergone.
Eric A. Erslev - One of the best experts on this subject based on the ideXlab platform.
-
Multiple geometries and modes of Fault-Propagation folding in the Canadian thrust belt
Journal of Structural Geology, 1997Co-Authors: Eric A. Erslev, Kyle R. MaybornAbstract:Abstract A multitude of fold models have been proposed to explain the variety of fold geometries which develop in front of thrust Faults. Detailed field, fabric, and photogrammetric studies of 4 Fault-cored asymmetrical folds in the thin-skinned Canadian thrust belt were used to test models of Fault-Propagation folding. Fold geometries include combinations of angular and rounded fold surfaces, highly contorted anticlinal hinge areas, and minimal penetrative deformation or changes in bedding thickness. Interlimb angles generally decrease with increasing shortening, indicating progressive fold tightening about fixed anticlinal hinges. Extensive flexural slip thrusting toward the anticlinal axes of angular folds suggests that kink folding in thin-skinned thrust belts is aided by material transfer from both fold limbs into hinge areas. Fold geometries change dramatically along the strike of individual structures, demonstrating the non-uniqueness of Fault-Propagation fold geometries. No single mode of Fault-Propagation folding can explain the diverse fold geometries seen in the Canadian thrust belt. This geometric variability can be ascribed to the complex interplay of multiple modes of folding. In strata near the causal thrusts, oblique shear and flexural slip in triangular shear zones distribute thrust displacements into both rounded and angular folds. Simultaneous angular folding of overlying strata commonly occurs by progressive kink folding where folds tighten by flexural slip on all fold limbs until the thrust breaks through the fold. Regional and local differences in the amount of pervasive, top-to-the-craton shear needed for progressive kink folding may be partially responsible for the variability of Fault-Propagation fold geometries in thin- and thick-skinned orogens world-wide.
-
ABSTRACT: Trishear Fault-Propagation Folding
1997Co-Authors: Eric A. ErslevAbstract:ABSTRACT Previous models of Fault-Propagation folding used kink-band geometries to approximate folding in front of propagating thrusts. However, kink-band kinematics cannot replicate the curved fold surfaces and complex strain patterns in natural and experimental Fault-Propagation folds, which also occur in front of steeper reverse and normal Faults. Fault-Propagation fold hinges tighten and converge downward, forming a triangular zone of penetrative deformation focused on the tip of the propagating Fault. The downward convergence of deformation in Fault-Propagation folds can be modeled as triangular shear zones. "Trishear," here defined as distributed, strain-compatible shear In a triangular (in profile) shear zone, provides an alternate kinematic model for Fault-Propagation folds. Trishear is analogous to simple shear in a tabular shear zone except that area balance in a triangular shear zone requires curved displacement oblique to the Fault slip direction. Incremental computer models of trishear folding can replicate many geometric features of Fault-Propagation folds, including variably curved fold hinges, downward-tightening fold surfaces, heterogeneous strains, and multiple Fault-Propagation trajectories.
-
Trishear Fault-Propagation folding
Geology, 1991Co-Authors: Eric A. ErslevAbstract:Previous models of Fault-Propagation folding used kink-band geometries to approximate folding in front of propagating thrusts. However, kink-band kinematics cannot replicate the curved fold surfaces and complex strain patterns in natural and experimental Fault-Propagation folds, which also occur in front of steeper reverse and normal Faults. Fault-Propagation fold hinges tighten and converge downward, forming a triangular zone of penetrative deformation focused on the tip of the propagating Fault. The downward convergence of deformation in Fault-Propagation folds can be modeled as triangular shear zones. "Trishear," here defined as distributed, strain-compatible shear in a triangular (in profile) shear zone, provides an alternate kinematic model for Fault-Propagation folds. Trishear is analogous to simple shear in a tabular shear zone except that area balance in a triangular shear zone requires curved displacement oblique to the Fault slip direction. Incremental computer models of trishear folding can replicate many geometric features of Fault-Propagation folds, including variably curved fold hinges, downward-tightening fold surfaces, heterogeneous strains, and multiple Fault-Propagation trajectories.
Yuming Jiang - One of the best experts on this subject based on the ideXlab platform.
-
Modeling and Quantifying the Survivability of Telecommunication Network Systems under Fault Propagation
2013Co-Authors: Lang Xie, Poul Heegaard, Yuming JiangAbstract:This paper presents a generic state transition model to quantify the survivability attributes of a telecommunication network under Fault Propagation. This model provides a framework to characterize the network performance during the transient period that starts after the Fault occurrence, in the subsequent Fault Propagation, and until the network fully recovers. Two distinct models are presented for physical Fault and transient Fault, respectively. Based on the models, the survivability quantification analysis is carried out for the system’s transient behavior leading to measures like transient connectivity. Numerical results indicate that the proposed modeling and analysis approaches perform well in both cases. The results not only are helpful in estimating quantitatively the survivability of a network (design) but also provide insights on choosing among different survivable strategies.
-
EUNICE - Modeling and Quantifying the Survivability of Telecommunication Network Systems under Fault Propagation
Lecture Notes in Computer Science, 2013Co-Authors: Lang Xie, Poul E. Heegaard, Yuming JiangAbstract:This paper presents a generic state transition model to quantify the survivability attributes of a telecommunication network under Fault Propagation. This model provides a framework to characterize the network performance during the transient period that starts after the Fault occurrence, in the subsequent Fault Propagation, and until the network fully recovers. Two distinct models are presented for physical Fault and transient Fault, respectively. Based on the models, the survivability quantification analysis is carried out for the system’s transient behavior leading to measures like transient connectivity. Numerical results indicate that the proposed modeling and analysis approaches perform well in both cases. The results not only are helpful in estimating quantitatively the survivability of a network (design) but also provide insights on choosing among different survivable strategies.
Mary Ford - One of the best experts on this subject based on the ideXlab platform.
-
Numerical modeling of trishear Fault Propagation folding
Tectonics, 1997Co-Authors: Stuart Hardy, Mary FordAbstract:In contrast to kink band migration modeling methods, trishear numerical models produce Fault Propagation folds with smooth profiles and rounded hinges. Modeled fold hinges tighten and converge downward, within a triangular zone of distributed deformation which is focused on the Fault tip. Such features have been reported from field studies and are also seen in analogue models of compressional deformation. However, apart from its initial application to Laramide folds, little quantitative work has been undertaken on trishear Fault Propagation folding in other settings. In addition, no study has been undertaken into the growth strata which might be associated with such structures. This paper uses an equivalent velocity description of the geometric model of trishear, together with models of erosion and sedimentation, to investigate trishear Fault Propagation folding of both pregrowth and growth strata. The trishear model is generalized to include a variety of Fault Propagation to slip ratios and Fault Propagation from a flat decollement. The models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata. When total slip on a structure is high, the model predicts overturned pregrowth and growth strata. During the initial stages of deformation, beds in the forelimb thicken but later thin when they become steep or overturned. The effect of variations in Fault Propagation to slip ratios on two‐dimensional finite strain in the models is assessed by the use of initially circular strain markers. High Fault Propagation to slip (p/s) ratios lead to narrow zones of high finite strain, while lower p/s ratios lead to more ductile deformation and broader zones of high strain. In all cases, hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating Fault. Modeled structures are compared with natural examples.
