Normal fault 3D geometry and displacement revisited: Insights from faults in the Norwegian Barents Sea

Torabi, Anita; Alaei, Behzad; Libak, Audun

doi:10.1016/j.marpetgeo.2018.09.032

Cited by 47 publications

(32 citation statements)

References 45 publications

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“…The second method, operating within a Bayesian inference scheme, is to incorporate the prior knowledge as a likelihood function to validate -or rather, as Tarantola (2006) states, invalidate -model realizations. This study focuses on the first method of applying prior knowledge from published structural geology literature (Torabi et al, 2019a) to parameterize the reasoning behind subjective inputs used for modeling fault zones in the MCUP formulation. This approach is demonstrated effectively in this study when considering the vertical termination depth of fault surfaces (Section 4.3).…”

Section: Mcup Formulationmentioning

confidence: 99%

“…To arrive at a more realistic approximation of the 3D fault geometry, a series of surfaces at fixed elevations are defined and used to terminate faults. The depth at which a fault is expected to terminate is based on prior knowledge obtained from past works into approximating the 3D geometry of faults (Walsh and Watterson, 1988;Nicol et al, 1996;Schultz and Fossen, 2001;Torabi et al, 2019a).…”

Section: Vertical Termination Depthmentioning

confidence: 99%

“…Fault zones may be irregular in shape, creating complex geometries which are difficult to characterize quantitatively (Torabi et al, 2019a, b). Peacock et al (2016) provide a detailed list of the various types of damage zones and intersecting fault networks that comprise the general term "fault zone".…”

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confidence: 99%

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Uncertainty assessment for 3D geologic modeling of fault zones based on geologic inputs and prior knowledge

Krajnovich¹,

Zhou²,

Gutierrez³

2020

Preprint

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Abstract. Characterizing the zone of damaged and altered rock surrounding a fault surface is highly relevant to geotechnical and reservoir engineering works in the subsurface. Evaluating the uncertainty associated with 3D geologic modeling of these fault zones is made possible using the popular and flexible input-based uncertainty propagation approach to geologic model uncertainty assessment – termed Monte Carlo simulation for uncertainty propagation (MCUP). To satisfy the automation requirements of MCUP while still preserving the key geometry of fault zones in the subsurface, a clear and straightforward modeling approach is developed based on four geologic inputs used in implicit geologic modeling algorithms (surface trace, structural orientation, vertical termination depth and fault zone thickness). The rationale applied to identifying and characterizing the various sources of uncertainty affecting each input are explored and provided using open-source codes. In considering these sources of uncertainty, a novel model formulation is implemented using prior geologic knowledge (i.e., empirical and theoretical relationships) to parameterize modeling inputs which are typically subjectively interpreted by the modeler (e.g., vertical termination depth of fault zones). Additionally, the application of anisotropic spherical distributions to modeling disparate levels of information available regarding a fault zone's dip azimuth and dip angle is demonstrated, providing improved control over the structural orientation uncertainty envelope. The MCUP formulation developed is applied to a simple geologic model built from historically available geologic mapping data to assess the independent sensitivity of each modeling input on the combined model uncertainty, revealing that vertical termination depth and structural orientation uncertainty dominate model uncertainty at depth while surface trace uncertainty dominates model uncertainty near the ground surface. The method is also successfully applied to a more complex model containing intersecting major and minor fault zones. The impacts of the model parameterization choices, the fault zone modeling approach and the effects of fault zone interactions on the final geologic model uncertainty assessment are discussed.

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Section: Mcup Formulationmentioning

confidence: 99%

Section: Vertical Termination Depthmentioning

confidence: 99%

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Uncertainty assessment for 3D geologic modeling of fault zones based on geologic inputs and prior knowledge

Krajnovich¹,

Zhou²,

Gutierrez³

2020

Preprint

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“…Displacement measurements in this study are data-driven and involve no interpretation. For detailed information on the fault extraction and datasets used in this study, the readers are referred to [18]. The displacement measurements have been considered as throw and not true displacement.…”

Section: Fault Data Extraction From Seismic Datamentioning

confidence: 99%

Statistical Analysis of Displacement and Length Relation for Normal Faults in the Barents Sea

et al. 2018

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This paper is devoted to the statistical analysis of dependence between fault length (L) and displacement (D). The main purpose of this work is to study the scaling relations between fault length and displacement using a database that includes datasets of 21 faults with geometric data extracted from 3D seismic coherence cubes of the Norwegian Barents Sea. Multiple linear regression and Bayesian and Akaike information criterions are applied to obtain optimal regression parameters. Our dataset is unique since it includes segment lengths of individual faults, unlike the previously published datasets. Hence, we studied both the dependence of fault segment length and accumulated fault length on displacement. The latter relation (accumulated fault length versus displacement) shows a general agreement (positive correlation and power-law relation) with the previously published results that are mainly obtained from outcrop studies, although the slopes vary for different lithologies. The differences could be attributed to the unique characteristics of our dataset that includes data of all segment lengths of individual faults.

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“…Structural studies have therefore often concentrated on defining displacement distributions as a means of investigating fault growth (e.g. Scholz et 40 al., 1993;Roche et al, 2012;Torabi et al, 2019), with fewer studies examining the geometries of associated fault-bend folds and the nature of strain partitioning along non-planar normal faults (e.g. Homberg et al, 2017).…”

Section: Introduction 20mentioning

confidence: 99%

Throw variations and strain partitioning associated with fault-bend folding along normal faults

Delogkos¹,

Saqab²,

Walsh³

et al. 2019

Preprint

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Normal faults have irregular geometries on a range of scales arising from different processes including refraction and segmentation. A fault with an average dip and constant displacement on a large-scale, will have irregular geometries on smaller scales, the presence of which will generate fault-related folds, with major implications for across-fault throw 10 variations. A quantitative model has been presented which illustrates the range of deformation arising from movement on fault surface irregularities, with fault-bend folding generating geometries reminiscent of normal drag and reverse drag. The model highlights how along-fault displacements are partitioned between continuous (i.e. folding) and discontinuous (i.e. discrete displacement) strain along fault bends characterised by the full range of fault dip changes. Strain partitioning has a profound effect on measured throw values across faults, if account is not taken of the continuous strains accommodated by 15 folding and bed rotations. We show that fault throw can be subject to errors of up to ca. 50% for realistic fault bend geometries (up to ca. 40°), even on otherwise sub-planar faults with constant displacement. This effect will provide apparently more irregular variations in throw and bed geometries that must be accounted for in associated kinematic interpretations. 1997;Tavani et al., 2005). This emphasis mainly derives from the importance of fault bends and associated ramp-flat 30

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Normal fault 3D geometry and displacement revisited: Insights from faults in the Norwegian Barents Sea

Cited by 47 publications

References 45 publications

Uncertainty assessment for 3D geologic modeling of fault zones based on geologic inputs and prior knowledge

Uncertainty assessment for 3D geologic modeling of fault zones based on geologic inputs and prior knowledge

Statistical Analysis of Displacement and Length Relation for Normal Faults in the Barents Sea

Throw variations and strain partitioning associated with fault-bend folding along normal faults

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