Critical state finite element models of contractional fault-related folding: Part 1. Structural analysis

Albertz, Markus; Lingrey, Steven

doi:10.1016/j.tecto.2012.05.015

Cited by 36 publications

(28 citation statements)

References 32 publications

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“…The style of folding observed in the mechanical models is in general agreement with the kinematics and deformation mechanisms implied by the kinkstyle fault-propagation folding models. These findings are consistent with recent finite-element-based mechanical models in which adaptive remeshing and an evolving strain-weakening constitutive model were employed (Albertz and Lingrey, 2012;Albertz and Sanz, 2012). Likewise, they are consistent with the observation from a range of previous DEM models that mechanical layer strength contrasts have a firstorder control on fault-related folding style for thick-skinned fault-propagation folds (Cardozo et al, 2005;Finch, 2006, 2007).…”

Section: Influence Of Mechanical Layering On Structural Stylesupporting

confidence: 90%

Insights into the mechanics of fault-propagation folding styles

Hughes¹,

Shaw²

2015

Geological Society of America Bulletin

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Fault-propagation folds are common structures that accommodate crustal shortening in various compressional settings worldwide. Motivated by the wide range of geometries observed for fault-propagation folds, we investigated the role played by mechanics in the variations observed for this structural class. Detailed structural measurements of a series of 15 fault-propagation folds from the Niger Delta, Argentina, and southeastern Asia reveal several relationships between aspects of the structural geometries. We found that the decrease in displacement updip along the fault is well approximated by a linear trend that has a relatively consistent slope, and that this gradient remains constant for increasing total displacement. This suggests that the faults propagate self-similarly, consistent with a range of kinematic models that have been used to describe them. Additionally, we observed that uplift has contributions both from rigid translation along a dipping fault and folding, and that the values observed for many natural structures lie between those predicted by the trishear and kink-style models, such as fixed-axis and constant-thickness fault-propagation folding. Finally, we found that fault-propagation folds exhibit a range of fault dips, with many structures having fault dips coincident with those characteristic of fault-bend folds, while another group is characterized by significantly higher fault dips. By developing a series of discreteelement mechanical models, we found that mechanical layering plays a first-order role in the development of different styles of faultpropagation folding. Homogeneous materials produce trishear-like fault-propagation folds, while strongly layered materials produce structures more similar to the kink-style kinematic models. Comparison with the observations from natural structures indicates that these mechanical models reproduce the observed trends, and that most natural structures fall between these two styles of models. This suggests that trishear and the kink-style (fixed-axis and constant-thickness) faultpropagation folding models may be thought of as end members on a continuum of possible fault-propagation folding geometries that are largely dictated by the degree of mechanical layer anisotropy in the stratigraphy. Finally, we suggest that fault steepening in highly anisotropic models may develop due to strain localization in tightly folded structural forelimbs. † Current address: Chevron Energy Technology Company, A Distance along fault Displacement B Figure 1. (A) Schematic depiction of a typical fault-propagation fold (adapted from Shaw et al., 2005), characterized by asymmetric limb widths and dips, a decrease in displacement along the thrust fault toward the fault tip (1) and an active synclinal axial surface pinned to the fault tip (2). (B) A decrease in displacement as a function of distance along the fault toward the fault tip.

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Section: Influence Of Mechanical Layering On Structural Stylesupporting

confidence: 90%

Insights into the mechanics of fault-propagation folding styles

Hughes¹,

Shaw²

2015

Geological Society of America Bulletin

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“…Structural style in shortening environments depends on numerous factors such as sediment strength, stress state, the existence of weak planes, sediment deposition, and the pore pressure regime (Albertz & Lingrey, ; Albertz & Sanz, ; Thornton & Crook, ). For example, Hubbert and Rubey () provide a mechanical explanation for the role of overpressure in overthrust faulting in which high overpressures decrease the effective stresses in detachments and, consequently, also decreases the frictional resistance, facilitating the slide of large masses of sediment.…”

Section: Resultsmentioning

confidence: 99%

“…The SR4 yield surface is composed of two different surfaces that intersect in a continuous manner at the peak stress. The cap side, where compaction is expected to take place, is defined by the Modified Cam Clay surface, whereas the shear side is defined by means of the Soft Rock 3 (SR3) constitutive model's surface (Albertz & Lingrey, ; Albertz & Sanz, ):

ϕ (p^{'}, ϵ_{v}^{p}) = g (θ, p^{'}) q + (p^{'} - p_{t}) \tan β 2.03em [\frac{(p^{'} - p_{c})}{(p_{t} - p_{c})} {2.03em]}^{1 / n}

for

p^{'} \geq p_{ϕ_{peak}}

and

ϕ (p^{'}, ϵ_{v}^{p}) = 1.19em [g (θ, p^{'}) {1.19em]}^{2} q^{2} - M_{ϕ}^{2} p_{ϕ_{peak}}^{2} 2.03em [1 - \frac{{(p_{ϕ_{peak}} - p^{'})}^{2}}{{(p_{ϕ_{peak}} - p_{c})}^{2}} 2.03em]

for

p^{'} < p_{ϕ_{peak}}

…”

Section: Model Setupmentioning

confidence: 99%

Hydromechanical Modeling of Stress, Pore Pressure, and Porosity Evolution in Fold‐and‐Thrust Belt Systems

et al. 2017

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We present coupled, critical state, geomechanical‐fluid flow simulations of the evolution of a fold‐and‐thrust belt in NW Borneo. Our modeling is the first to include the effects of both syntectonic sedimentation and transient pore pressure on the development of a fold‐and‐thrust belt. The present‐day structure predicted by the model contains the key first‐order structural features observed in the field in terms of thrust fault and anticline architectures. Stress predictions in the sediments show two compressive zones aligned with the shortening direction located at the thrust front and back limb. Between the compressive zones, near to the axial plane of the anticline, the modeled stress field represents an extensional regime. The predicted overpressure distribution is strongly influenced by tectonic compaction, with the maximum values located in the two laterally compressive regions. We compared the results at three notional well locations with their corresponding uniaxial strain models: the 2‐D thrust model predicted porosities which are as much as 7.5% lower at 2.5 km depth and overpressures which are up to 6.4 MPa higher at 3 km depth. These results show that one‐dimensional methods are not sufficient to model the evolution of pore pressure and porosity in contractional settings. Finally, we performed a drained simulation during which pore pressures were kept hydrostatic. The predicted geological structures differ substantially from those of the coupled simulation, with no thrust faulting. These results demonstrate that pore pressure is a key control on structural development.

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“…Geomechanical modelling can be employed in conjunction with advanced constitutive models to simulate sediment rheology which are capable of accounting for the full 3D stress tensor and its impact on compaction (Albertz and Lingrey, 2012;Albertz and Sanz, 2012;Luo et al, 2012;Smart et al, 2012) and overpressure generation Thornton and Crook, 2014).…”

Section: Introductionmentioning

confidence: 99%

Assessing the implications of tectonic compaction on pore pressure using a coupled geomechanical approach

Obradors-Prats

Rouainia

Aplin

et al. 2017

Marine and Petroleum Geology

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractOverpressure prediction in tectonic environments is a challenging topic. The available pore pressure prediction methods are designed to work in environments where compaction is mostly one dimensional and driven by the vertical effective stress applied by the overburden. Furthermore, the impact of tectonic deformation on stresses, porosity and overpressure is still poorly understood. We use a novel methodology to capture the true compaction phenomena occurring in an evolving 3D stress regime by integrating a fully-coupled geomechanical approach with a critical state constitutive model. To this end, numerical models consisting of 2D plane strain clay columns are developed to account for compaction and overpressure generation during sedimentation and tectonic activity. We demonstrate that a high deviatoric stress is generated in compressional tectonic basins, resulting in a substantial decrease in porosity with continuing overpressure increase.The overpressure predictions from our numerical models are then compared to those estimated by the equivalent depth method (EDM) in order to quantify the error induced when using classical approaches, based on vertical effective stress, in tectonic environments. The stress paths presented here reveal that a deviation from the uniaxial burial trend can substantially reduce the accuracy of the EDM overpressure predictions.

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Critical state finite element models of contractional fault-related folding: Part 1. Structural analysis

Cited by 36 publications

References 32 publications

Insights into the mechanics of fault-propagation folding styles

Insights into the mechanics of fault-propagation folding styles

Hydromechanical Modeling of Stress, Pore Pressure, and Porosity Evolution in Fold‐and‐Thrust Belt Systems

Assessing the implications of tectonic compaction on pore pressure using a coupled geomechanical approach

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