Anita Torabi

• Oliveira, Lorenna Sávilla Brito; Lucas, Luiza Cavalcante Vinhas; Iacopini, David; Balsamo, Fabrizio; Torabi, Anita & Alaei, Behzad [Show all 11 contributors for this article] (2026). Structural control and geometric characterization of a hydrothermal vent complex using seismic data, Potiguar Basin – Brazil. Journal of South American Earth Sciences. ISSN 0895-9811. 184. doi: 10.1016/j.jsames.2026.106255. Full text in Research Archive
• Mikołajewska, Weronika; Torabi, Anita & Puskarczyk, Edyta (2026). Multiscale subsurface structural study – insights from the polish part of the Southern Permian Basin. Journal of Structural Geology. ISSN 0191-8141. 202. doi: 10.1016/j.jsg.2025.105568. Full text in Research Archive
• Berstad, Magnus Ketilson Rykke; Torabi, Anita; Silio, Ofelia Soledad; Basa, Abhisek & García-Tortosa, Francisco Juan (2025). Relation between seismites and active faulting. Physics and Chemistry of the Earth. ISSN 1474-7065. 141. doi: 10.1016/j.pce.2025.104167. Full text in Research Archive Show summary

  Seismites occur during an earthquake in soft sediments, when seismic energy increases pore water pressure beyond the overburden pressure, reducing cohesion, and hence deforming the sediments. Therefore, the presence of seismites could reveal the magnitude of an earthquake, although the kinematic and mechanical relation between the active faults and seismites have not been previously understood. In southern Spain, within the Guadix-Baza basin, seismites are found in close proximity to the active Galera fault (GF) and Baza fault (BF) in three localities, Galera, Pilares and Cúllar. This study aims to determine if the location of seismites relative to the active fault, controls seismites spacing, orientation, size, and geometry. A multi-scale approach was used, integrating drone-based photogrammetry, outcrop studies of the geometry and mechanical properties of seismites (Young's moduli). Our results reveal a consistent alignment of the seismites strike with nearby segments of the GF. Furthermore, we observe a variation in the size and frequency of seismites along the fault damage zone. We observed color variations within the concentric layers of seismites (grey and red) that have different Young's moduli values and vary between the studied localities in Pilares and Galera. Our results show that slight variations in the depth of depositional environment of the lacustrine sediments and changes in the mineralogy, together with the positioning of seismites relative to GF and BF likely contribute to the observed differences in seismite characteristics across the investigated localities. Our findings enhance the understanding of fault-seismite relationships and using seismites as past seismicity indicators.

• Basa, Abhisek; Alaei, Behzad & Torabi, Anita (2025). Detailed 3D characterization of fault geometric attributes: Insights from deep learning-based fault imaging in seismic data. Journal of Structural Geology. ISSN 0191-8141. 203. doi: 10.1016/j.jsg.2025.105569. Full text in Research Archive Show summary

  Generation of 3D fault network in conventional seismic interpretation involves creation of structural models by manually tracking the same discontinuity across seismic horizons on several adjacent vertical profiles. This process is often time-consuming, susceptible to human bias and introduces uncertainties in the characterization of fault geometric attributes - such as length, width and throw - that cannot be reliably quantified. In this study, we adopt a data-driven approach and extract the geometric attributes of the individual segments constituting the 3D seismic fault zone architecture in remarkable detail, that provides insights beyond the capabilities of conventional seismic attributes. This is achieved through the application of 3D Deep Learning (DL) Networks trained on 3D synthetic seismic datasets on a seismic survey from the eastern flank of Polhem Subplatform, SW of Norwegian Barents Sea to automatically create probabilistic fault volumes. Detailed extraction of individual fault segments from the fault probability volume allows us to investigate the seismic fault zone architecture at multiple scales. Our results show that the maximum segment length of all the studied faults is present near the upper tips and reduces towards the lower tips. The fault zone widths of individual segments measured on E-W-oriented vertical scanplanes orthogonal to the strike of the dominant fault set mostly vary between 10 and 20m. They exhibit higher values at locations where fault segments link laterally/vertically or interact with antithetic fault sets with similar strike of the dominant westward dipping fault set. Throw estimates and the total accumulated fault zone widths are higher towards the lower tips of the faults. Thus, the application of Deep Learning enables data-driven, high-resolution visualization of the seismic fault zone architecture and facilitates comprehensive extraction of fault geometric attributes, providing a more robust complement to traditional interpretation techniques.

• Ghione, Federica; Palacios, Sergio Molina; Torabi, Anita & Oye, Volker (2025). Evaluating earthquake impacts in oslo, norway: a multi-method approach. Natural Hazards. ISSN 0921-030X. 121, p. 19781–19809. doi: 10.1007/s11069-025-07588-3. Full text in Research Archive Show summary

  In this study, we conducted a comprehensive seismic risk assessment for Oslo (capital of Norway), integrating both deterministic and probabilistic approaches to capture a holistic view of potential earthquake impacts. Based on the field data from exposed major faults in the Oslo rift margin and historical earthquakes in this region, the deterministic analysis examined three scenarios: (i) an Mw 5.4 earthquake that occurred in 1904 in the Oslo rift zone; (ii) a hypothetical Mw 6.0 event on the east side of the rift zone (Østmarka event), and (iii) a hypothetical Mw 6.0 event along an exposed fault zone in the central rift zone (Nesodden event). Among the three scenarios, the Østmarka event resulted in the highest losses, while the 1904 scenario showed negligible impact. In both the Østmarka and the 475-year return period probabilistic scenarios, Sentrum and Frogner neighbourhoods consistently emerged as the most affected areas. This is primarily due to a combination of local soil conditions and the prevalence of unreinforced masonry buildings, highlighting the critical interplay between physical hazard and locally specific vulnerability associated with the neighbourhood’s particular characteristics. The combination of deterministic and probabilistic approaches offers a detailed and nuanced understanding of seismic risks in Oslo. The findings underscore the need for targeted mitigation efforts and preparedness strategies, particularly in neighbourhoods that are more susceptible to seismic risks. By integrating these comprehensive risk assessments, the study provides valuable insights into the uneven distribution of seismic risk across Oslo. The results aim to inform local authorities and policymakers, aiding in the development of effective strategies to enhance the resilience of the city’s infrastructure and population against future seismic events.

• Qu, Yuanwei; Waaler, Arild Torolv Søetorp; Torabi, Anita & Zhou, Baifan (2025). Challenges and Approach: AI for Digitalised Carbon Storage Analysis. CEUR Workshop Proceedings. 3975. Full text in Research Archive Show summary

  Carbon Capture and Storage (CCS) plays an essential role in mitigating climate change. A comprehensive CO2 storage analysis is key to CCS success, however, its advancement is hindered by interdisciplinary complexities, data fragmentation, and the need for enhanced transparency. This paper presents ongoing work in an integrated digitalisation framework for CO2 storage analysis that addresses three major challenges: knowledge complexity across geosciences, reservoir engineering, and computer science; the heterogeneous, multi-scale nature of geological data; and the requirement for explainable decision-making in high-risk subsurface storage scenarios. Our approach leverages both symbolic AI and generative AI. On the symbolic AI side, it includes ontologydriven knowledge engineering to harmonise domain-specific terminologies, and employs a layered information modelling and data integration system to standardise diverse datasets. Additionally, a generative AI-powered query and explanation system provides context-aware, transparent analyses. This framework aims to streamline multidisciplinary collaboration and enhance the accountability and reliability of long-term CO2 storage, thereby supporting the transition to a carbon-neutral future

• Dichiarante, Anna Maria; Torgersen, Espen; Redfield, Thomas Fitzmaurice; Köhler, Andreas; Torabi, Anita & Svendby, Anne Kathrine [Show all 7 contributors for this article] (2025). Spectral Analysis of Topography as Proxy for Lineament Analysis. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 130(2). doi: 10.1029/2024JB029790. Full text in Research Archive Show summary

  Spectral analysis (SA) for image processing, utilizing the Fast Fourier Transform (FFT), computes the 2D power spectrum to capture the amplitude of each frequency component of an image. Recent studies have applied SA on digital elevation models (DEMs) to characterize repetitive and spatially homogeneous landforms in terms of their orientation, frequency, and amplitude. Here, we advance the application of SA by introducing a new preprocessing step and an appropriate windowing function, tailored to analyze heterogenous and complex topographies and derive lineament spatial distributions. The validation of our approach involved two phases: (a) testing on synthetic images, and (b) application to a case study. The synthetic image validation illustrated the length-weighted characteristics of SA-derived rose diagrams and the robustness of the method, evidenced by a 99% similarity across 1,000 synthetically generated lineament networks. The case study consisted of three areas characterized by different topographic patterns within the Oslo region of Norway. The SA-derived results were compared to lineaments automatically extracted using a conventional peak-and-valley seeking algorithm that mimics manual tracing of lineaments inside a 3D map domain. The comparison showed similarity better than 90%. Lastly, we addressed a key pitfall of SA by locating signatures observed in the power spectrum on the map through cross-correlation (CC) of profiles. Although CC results are not consistently perfect, they provide a promising avenue for further development.

• Basa, Abhisek; Torabi, Anita; Jiménez-Millán, Juan; Alaei, Behzad & García-Tortosa, Francisco Juan (2025). Unraveling the key factors controlling active faulting in Tertiary and Quaternary sequences. Earth and Planetary Science Letters. ISSN 0012-821X. 656. doi: 10.1016/j.epsl.2025.119268. Full text in Research Archive Show summary

  The effects of across-fault variation of mechanical properties and along-fault lithological heterogeneity on the seismicity of active faults is poorly understood. Moreover, the role of chemical processes on the mechanical behavior of active faults has not yet received sufficient attention. Such phenomena have more relevance, especially when faults juxtapose chemically reactive carbonate-dominated host rocks. In this study, we examine the key controls on active faulting by utilizing excellent outcrops of an intrabasinal strike-slip fault cutting across Tertiary and Quaternary sequences. We integrate structural, geomechanical and mineralogical investigations of faults and adjacent host rocks geographically exposed at different structural positions along the length of a 30 km-long, NE-SW-striking Galera Fault (GF) in Guadix-Baza basin, SE Spain. Our results show that fault and host rocks along the GF become carbonate-rich predominantly consisting of calcite towards NE. The thickness of sedimentary cover increases towards SW, where gypsum and phyllosilicate minerals are dominant. Calcite precipitation in fault rocks leads to reduction of porosity and significant enhancement of P-wave velocity (Vp), relative to the adjacent host rocks, and makes the fault zone more prone to seismic slip. On the contrary, phyllosilicates including clay mineral assemblages reduce the strength of the fault rocks and promote aseismic creep. The relationship between Vp and modified estimate of Brittleness Index used in this study indicate that the mineral assemblage of the fault as well as the adjacent host rocks influence seismicity. Our novel approach predicts more seismic activity towards the NE-part of GF due to dominance of calcite-rich rocks and proximity to the basement. This is validated by earthquake records in the studied area, which document shallow earthquakes concentrated towards the NE-part of GF. Thus, our study highlights the importance of adopting interdisciplinary approaches and understanding of the basin architecture controlling the distribution of host rocks to comprehend complex processes associated with active faulting.

• Labry, Cyrill; Funedda, Antonio; Torabi, Anita; Arras, Claudio & Pelo, Stefania Da (2025). Deformation style and fluid flow behaviour in a faulted siliciclastic-carbonate sequence. Journal of Structural Geology. ISSN 0191-8141. 199. doi: 10.1016/j.jsg.2025.105468. Full text in Research Archive Show summary

  Understanding fluid flow behaviour of faults is important for resource exploitation and management. Most studies analysing fluid flow behaviour in fault zones focus on either high-porosity or low-porosity sequences. In this study, we analyse various mechanical layers within alternating siliciclastic-carbonate sequences in fault zones in the Oligo-Miocene Logudoro basin, located in northern Sardinia (Italy). We combined a variety of methods, including field measurements of structures, in-situ permeability and Schmidt Hammer rebound measurements converted to uniaxial compressive strength. Furthermore, we performed thin section analysis, to characterize grain size, porosity, and mineral compositions. We used the gathered data to model the fluid flow conditions within deformation patterns present in one fault-zone. Deformation styles are related to mechanical properties of the rocks at the time of faulting, juxtaposition and differences in intergranular space and porosity in sandstones. The permeability is influenced by the presence of deformation structures such as fractures (high permeability), compactional shear bands (low permeability) and fault rocks within fault core (high and/or low permeability). The fluid flow model highlights the significant influence of deformation bands on the flow field and hydraulic gradient, demonstrating the importance of including these structures in the analysis.

• Torabi, Anita; Alaei, Behzad & Smith, Adrian (2024). Fault characteristics in exhumed basement rocks; implications for understanding subsurface basement faults. Tectonophysics. ISSN 0040-1951. 887. doi: 10.1016/j.tecto.2024.230445. Full text in Research Archive Show summary

  We studied fault core geometry and mechanical properties of exhumed basement rocks at two localities (Storskora and Lislaskora) in Sotra Island, western Norway. We combine outcrop studies with in-situ measurements of the rock stiffness (Young's modulus) to characterize the faults. Faults were investigated both along and across strike using multiple 1D scanlines on the outcrop. Our results show that both fault core thickness and stiffness values vary along the faults. Thicker fault cores (up to 0.8 m and 1.9 m in Storskora and Lislaskora loaclities, respectively) show higher values of stiffness (Young's modulus) up to 70 GPa. The stiffness values of the fault core are generally higher than those measured on the damage zone of the faults in this area. The presence of epidote and compacted fault gouge in the fault core can cause the increase in estimated fault core stiffness. In contrast, fractures are dominant in the damage zones causing local reductions in the stiffness. A map of recent seismic events in this area shows potential seismic activities along some of the major exposed faults in the Sotra Island (e.g. Rustefjorden Fault). Based on the evidence from outcrop, inferred displacements, and interpretation of an available reflection seismic section, we found that the exposed faults could be secondary and part of the damage zone of the Øygarden Fault Complex in the east margin of the rift system in the North Sea. The results of this study could be utilized to predict the architecture and changes in rock stiffness of basement-involved faults in the subsurface.

• Oliveira, L.S.B.; Nogueira, F.C.C.; Vasconcelos, D.L.; Torabi, Anita; Alaei, Behzad & Balsamo, F. [Show all 8 contributors for this article] (2024). Seismic and outcrop-based 3D characterization of fault damage zones in sandstones, Rio do Peixe Basin, Brazil. Journal of Structural Geology. ISSN 0191-8141. 189. doi: 10.1016/j.jsg.2024.105276. Full text in Research Archive
• Alaei, Behzad & Torabi, Anita (2024). Fault asperity and roughness, insight from faults in 3D reflection seismic data. Marine and Petroleum Geology. ISSN 0264-8172. 170. doi: 10.1016/j.marpetgeo.2024.107145. Full text in Research Archive Show summary

  The complexity of faults and the bias in the gathered fault data from different sources such as outcrops, reflection seismic data and earthquakes causes uncertainty to the understanding of fault plane geometry at the seismic scale, among other fault geometric attributes. Fault plane roughness and irregularities at different scales are important geometric attributes caused by asperities, which are linked to the fault frictional behaviour and mechanics. Asperities are localized areas with higher strength on the fault plane, which resist the applied stress to a certain limit before the fault ruptures. Imaging faults’ real geometry can help us to gain more insight into the fault roughness and asperities, thereby enhancing our understanding of the mechanics of faulting and earthquakes. In this study, for the first time, we map fault asperities and roughness on seismic scale faults using their 3D structures extracted from reflection seismic data. We have studied 21 normal faults ranging in depth from about 0.5 to 3 km with clastic dominated lithology and some carbonates by extracting and characterizing their true fault plane geometry on 3D reflection seismic data using Gaussian filtered coherency attributes and measuring throw over the entire fault plane. The outline of the mapped asperities is the envelope of internal tip-points between the segments on the fault plane 3D structure. Our results show that in most cases, at the boundary of the asperities, the strike of fault internal segments changes and the throw increases. We have introduced two new attributes characterizing fault plane roughness at seismic scale, notably 2D roughness attribute and segment mean roughness. The variations of these two attributes, i.e. higher values near the asperity boundary, have close link to the locations of asperities on the fault planes.

• Qu, Yuanwei; Kamburjan, Eduard; Torabi, Anita & Giese, Martin (2024). Semantically triggered qualitative simulation of a geological process. Applied Computing and Geosciences. 21. doi: 10.1016/j.acags.2023.100152. Full text in Research Archive
• Basa, Abhisek; Torabi, Anita; Vasconcelos, David L.; Bezerra, Francisco H.R. & Nogueira, Francisco C.C. (2024). Architecture of interacting deformation band fault zones in siliciclastic rocks and its influence on geomechanical property distribution. Tectonophysics. ISSN 0040-1951. 875. doi: 10.1016/j.tecto.2024.230226. Full text in Research Archive Show summary

  Spatial organization of strain-hardening zones and the adjacent damage zones associated with faulting of porous siliciclastic rocks influence the across-strike variation of geomechanical properties. The across-fault geomechanical property distribution is expected to change when fault zones of distinct orientations interact. We performed outcrop-scale structural analysis along scanlines trending perpendicular to fault strike to constrain the extent of fault zones oriented dominantly along NE-SW and NW-SE. Young's Modulus (E) and P-wave velocity (Vp) measurements on deformation bands (DBs) and host rocks along such scanlines are further utilized to better characterize the fault zones. The selected outcrop exposes Cretaceous siliciclastic rocks in Rio do Peixe Basin, NE Brazil. In this study, Vp measurements coupled with detailed structural investigation have been integrated with grain size analysis for the first time. We observe that DBs oriented parallel to the major fault sets show grain size reduction along with higher E and Vp relative to the adjacent host rocks, indicating cataclasis and strain-hardening. The expected variation of geomechanical properties across the relatively late-stage NE-SW-trending fault zones gets obscured at sites of intense interaction with the early formed NW-SE-striking fault zones. In such areas, E of DBs consistently increases with proximity to the NW-SE-oriented fault zones revealing that the structural position of pre-existing fault zones mostly controls the geomechanical property distribution at sites of intense fault interaction. Similarly, we observe a direct relationship between Vp and grain size of the host rocks across the late-stage faults where there is relatively less fault interaction. However, this relationship does not exist within zones of intense fault interaction. As DBs are prevalent mostly in coarse-grained rocks, Vp in coarse-grained host rocks increases with proximity to the constrained fault zones. An integrated approach adopted in our study is crucial in delineating the effects of fault interaction on the distribution of geomechanical properties.

• Bönke, Wiktor; Alaei, Behzad; Torabi, Anita & Oikonomou, Dimitrios (2024). Data augmentation for 3D seismic fault interpretation using deep learning. Marine and Petroleum Geology. ISSN 0264-8172. 162. doi: 10.1016/j.marpetgeo.2024.106706. Full text in Research Archive Show summary

  Manual seismic interpretation of faults is a tedious and complicated process, which is prone to human error and bias. A semi-automatic approach for interpreting faults on seismic data is to use attributes that highlight discontinuities. These methods need to be optimized by the interpreter, thus constantly rely on the interpreter's knowledge. Recently, Machine Learning (ML) techniques in general and Convolutional Neural Networks (CNN) as part of Deep Neural Networks (DNN), in particular, have been used to detect and image faults on seismic data in order to make the process more automated and accurate. Supervised CNN learns and evolves from manually annotated or labeled fault interpretations. In this study, we have applied supervised 2D CNN to image faults on seismic data through binary segmentation. The study was performed on 3D marine seismic surveys in off-shore Norway collected from three separate locations along the Norwegian Continental Shelf, utilizing Efficient UNET CNN architecture. We applied data augmentation (geometric transformations) and hyperparameter tuning to improve the learning process and performance of the deep learning algorithm. We used noise content, acquisition type, imaging type, and fault scale as the main criteria to select seismic surveys. The application of data augmentation to the training and testing data generally led to improvement in the performance of 2D CNN on fault predictions, although the amount of improvement varied with respect to different surveys. The initial 2D CNN fault prediction improvement mainly relied on the quality, and size of faults present in the 3D seismic volumes. Further, improvement was achieved by the adjustment of certain hyperparameters affecting the training and testing process of the 2D CNN. However, we found little to no improvement on one seismic volume containing high levels of noise.

• Qu, Yuanwei; Perrin, Michel; Torabi, Anita; Abel, Mara & Giese, Martin (2023). GeoFault: A well-founded fault ontology for interoperability in geological modeling. Computers & Geosciences. ISSN 0098-3004. 182. doi: 10.1016/j.cageo.2023.105478. Full text in Research Archive Show summary

  Geological modeling currently uses various computer-based applications. Data harmonization at the semantic level using ontologies is essential to make these applications interoperable. Since geo-modeling is part of several multidisciplinary projects, interoperability requires semantic harmonization to exchange information between geological applications and integrate other domain knowledge at a general level. Therefore, domain ontologies that describe geological knowledge must be based on a sound ontological background to ensure this knowledge is integrable. Faults are essential for understanding and solving structural problems but are complex to model because the concept of fault includes a group of geological entities with a distinct ontological nature. A fault can correspond to thin, deformed rock volumes or spatial arrangements resulting from the displacement of geological blocks, but at a broader scale, geologists describe faults as surfaces or components of complex fault arrays. Our work intends to harmonize these views by presenting a domain ontology, GeoFault, resting on the Basic Formal Ontology (BFO) and the GeoCore ontology. GeoCore and GeoFault support the parametric description of geological sites as a preliminary step for quantitative and qualitative analysis. We have proposed GeoFault after systematically revising the literature and several knowledge-acquisition sessions with expert structural geologists. The ontology formalizes a vocabulary for fault “sensu stricto,” excluding ductile shear deformations. It covers the regional to outcrop scales, excluding structures at the microscopic, orogenic, and tectonics scales, and it avoids interpretive language associated with geological processes as far as possible. Extending the BFO and GeoCore ontologies allows the fault concept to be related to formal ontological classes in a consistent semantic-rich framework. The ontology artifact is implemented in OWL 2, validated by competency questions with two use cases, and tested using an in-house ontology-driven data entry application. The GeoFault ontology is publicly available and provides a solid framework for clarifying fault knowledge and a foundation for many applications.

• Torabi, Anita; Rudnicki, John; Alaei, Behzad & Buscarnera, Giuseppe (2023). Envisioning faults beyond the framework of fracture mechanics. Earth-Science Reviews. ISSN 0012-8252. 238. doi: 10.1016/j.earscirev.2023.104358. Full text in Research Archive Show summary

  Faults are complex structures that substantially influence the mechanical behavior and hydraulic connectivity of rock formations. Therefore, studying faults is important for a variety of disciplines such as geoscience, civil, geotechnical, reservoir engineering, and material science among others. Researchers from these disciplines have considered different aspects of faults, namely geometry, petrophysical properties and mechanics. Until now, these studies have evolved separately and at different scales, making it difficult to connect the geometric development of fault structure to its mechanics. The current understanding of fault geometry and growth is based on fracture mechanics and on many qualitative and quantitative studies on outcrop and seismic reflection surveys among other datasets. The application of fracture mechanics theory is mostly confined to simple geometries: elliptical models for a single fault plane and uniform properties. These applications predict the maximum displacement at the center of the fault, which is not in agreement with the new findings from 3D seismic and outcrop studies. These fracture mechanics models emphasize fault propagation along strike (in 2D). Although they can include the presence of a process zone at the fault tip, the models fail to explain the development of cross-fault damage zones and localization within the fault core as well as fault segmentation and displacement partitioning. Therefore, it is timely to revise the existing applications of fracture mechanics to simple fault geometries and to develop a data-driven fault mechanics possessing closer agreement with real, observed subsurface heterogeneity. This would allow better prediction of fault geometry, propagation, and growth in 3D. We suggest recent advances in non-destructive numerical characterization of faults and application of Deep Neural Networks (DNN) to map fault geometry and predict its properties from seismic data enable us for the first time to extract simultaneously faults' geometrical and mechanical properties at an unprecedented speed and accuracy, thus resolving the 3D fault shape and properties in ways that were unthinkable just a decade ago.

• Brito, Lorenna Sávilla B.; Alaei, Behzad; Torabi, Anita; Leopoldino-Oliveira, Karen M.; Vasconcelos, David Lino & Bezerra, Francisco Hilário Rego [Show all 7 contributors for this article] (2023). Automatic 3D fault detection and characterization — A comparison between seismic attribute methods and deep learning. Interpretation. ISSN 2324-8858. 11(4), p. T793–T808. doi: 10.1190/INT-2023-0016.1. Full text in Research Archive
• Torabi, Anita (2023). Understanding and modelling brittle deformation in the earth: insight from a novel experimental approach. First Break. ISSN 0263-5046. 41(7), p. 75–79. doi: 10.3997/1365-2397.fb2023057. Full text in Research Archive Show summary

  Current experimental approaches on faults provide a significant contribution to our understanding of brittle deformation in the crust. However, they rarely present a multiscale view of fault initiation, propagation and growth or the complex geometry of natural faults combined with other geological features such as folds and flow structures. We suggest new types of experiments that are inspired by the observations of natural phenomena on the water surface of a lake. In order to create similar structure to the nature, we have investigated different possibilities, hence designed and run the first series of novel experiments in a large water tank setup at the hydrodynamics laboratory of the University of Oslo. The water tank is equipped with cameras to dynamically image the experimental process. Using capillary waves and added impurity (pollen) to the water surface in a controlled laboratory set-up, our experiments created structures similar to faults, folds, and flow structures observed in nature. We suggest that these experiments can be utilised to not only study the fault growth process but also to answer some fundamental questions with regard to material properties such as friction and the stress configuration needed to create brittle and ductile deformation in the Earth.

• Khoirrashif, Khoirrashif; Rahman, Md Jamilur; Bohloli, Bahman; Torabi, Anita & Mondol, Md Nazmul Haque (2022). Machine learning application for compressional wave velocity log prediction in Sleipner CO2 storage, offshore Norway. 83rd EAGE Annual Conference & Exhibition. EarthDoc. doi: 10.3997/2214-4609.202210408. Full text in Research Archive
• Libak, Audun; Torabi, Anita & Alaei, Behzad (2022). Normal fault geometric attribute variations with lithology: examples from the Norwegian Barents Sea. Geological Society Special Publication. ISSN 0305-8719. 495(1), p. 7–27. doi: 10.1144/SP495-2018-164. Full text in Research Archive Show summary

  The geometry of faults exposed in the field is at least partly controlled by host-rock lithology. However, little work has been published on the effect of lithology on the geometry of very large faults imaged in seismic data. This paper presents such a study for seismic-scale faults in the Norwegian Barents Sea. Gamma-ray data are used to extract clay volumes of the host rock. These clay volume logs are used to populate 3D seismic cubes with lithology information. Finally, the clay volume cubes are co-rendered with seismic coherence cubes using opacity blending. This makes it possible to visualize both...

• Shahin, Ghassan; Torabi, Anita; Rudnicki, John & Buscarnera, Giuseppe (2021). The Role of Stratigraphy and Loading History in Generating Complex Compaction Bands in Idealized Field-Scale Settings. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 126(2). doi: 10.1029/2020JB020452. Full text in Research Archive
• Skurtveit, E.; Torabi, Anita; Sundal, Anja & Braathen, A. (2021). The role of mechanical stratigraphy on CO<inf>2</inf> migration along faults – examples from Entrada Sandstone, Humbug Flats, Utah, USA. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 109. doi: 10.1016/j.ijggc.2021.103376. Full text in Research Archive Show summary

  Bleaching patterns along a faulted succession provides new insight into fluid migration pathways controlled by the fault zone and mechanical stratigraphy. In order to investigate this effect, we logged stratigraphic layers in Humbug Flats, Utah, USA both in host rocks and faulted rocks, where a 40 m offset normal fault cuts through the Entrada Sandstone. We measured petrophysical and mechanical properties using TinyPerm II, Schmidt Hammer and laboratory core testing for selected layers. Bleaching has been identified as a proxy for fluid migration parallel to bedding, which fades out with distance from faults. A new observation is that fracturing of bed interfaces contributes to horizontal flow out from the fault zone. Longer-distance comprehensive bleaching dominates the most permeable beds (units), hosting porosity-controlled deformation band associated to fault zones. Fractures prevail in low permeability and stiffer units, where isolated fracture parallel bleaching haloes are observed within fault damage and process zones. Strong correlation is observed between permeability/porosity and stiffness/strength properties for the tested samples of different layers along the stratigraphic logs. For the studied fault, fractures provide important conduits for vertical flow across low permeability and stiff layers, whereas the more porous layers provide bedding-parallel flow paths out of the fault zone.

• Souza, Daniel Henrique Silva de; Nogueira, Francisco Cézar Costa; Vasconcelos, David Lino; Torabi, Anita; Souza, Jorge André Braz de & Nicchio, Matheus Amador [Show all 8 contributors for this article] (2021). Growth of cataclastic bands into a fault zone: A multiscalar process by microcrack coalescence in sandstones of Rio do Peixe Basin, NE Brazil. Journal of Structural Geology. ISSN 0191-8141. 146. doi: 10.1016/j.jsg.2021.104315. Full text in Research Archive
• Torabi, Anita; Balsamo, Fabrizio; Nogueira, Francisco C.C.; Vasconcelos, David L.; Silva, Amanda C.E. & Bezerra, Francisco H.R. [Show all 7 contributors for this article] (2021). Variation of thickness, internal structure and petrophysical properties in a deformation band fault zone in siliciclastic rocks. Marine and Petroleum Geology. ISSN 0264-8172. 133. doi: 10.1016/j.marpetgeo.2021.105297. Full text in Research Archive Show summary

  We studied the geometry and petrophysical properties of fault core and damage zones of a deformation band fault zone in the arkosic sandstones of the Cretaceous Antenor Navarro Formation in the Rio do Peixe Basin, Brazil. The present work includes results from fieldwork and laboratory measurements. We performed structural, geometric, and permeability measurements in the field. These measurements were performed on a longitudinal scanline along the fault core and 18 orthogonal scanlines crossing both fault core and damage zones in the footwall and hanging wall. Drone images were taken from the field locality to study the geometric relation between fault core and individual deformation bands in the damage zone. Porosity, capillary pressure and grain size analyses were performed on the samples. The studied fault is normal and composed of three linked segments, a central E-W segment which is hard-linked to two NE-SW segments tipping toward east and west. Our results show that fault core is the thickest on the E-W segment. The damage zone is narrower around the central part (E-W segment) of the fault and widens westward in both hanging wall and footwall, beyond this point the hanging wall damage zone is wider than the footwall damage zone. The thickest part of fault core has the lowest porosity and permeability and the highest capillary threshold pressure, therefore, increasing the fault sealing capacity. Permeability measurements parallel and perpendicular to fault dip show an anisotropy, in which the permeability perpendicular to fault dip is one order of magnitude lower than dip-parallel permeability measurements. This work highlights the effect of hard linkage between the E-W and NE-SW segments of the studied fault on the petrophysical properties of fault rocks and emphasizes the influence of such linkage on hampering the fluid flow along the breached segment of the fault.

• Medici, Giacomo; Smeraglia, Luca; Torabi, Anita & Botter, Chartlotte (2020). Review of Modeling Approaches to Groundwater Flow in Deformed Carbonate Aquifers. Ground Water. ISSN 0017-467X. doi: 10.1111/gwat.13069. Full text in Research Archive Show summary

  We discuss techniques to represent groundwater flow in carbonate aquifers using the three existing modeling approaches: equivalent porous medium, conduit network, and discrete fracture network. Fractures in faulted stratigraphic successions are characterized by dominant sets of sub‐vertical joints. Grid rotation is recommended using the equivalent porous medium to match higher hydraulic conductivity with the dominant orientation of the joints. Modeling carbonate faults with throws greater than approximately 100 m is more challenging. Such faults are characterized by combined conduit‐barrier behavior. The barrier behavior can be modeled using the Horizontal Flow Barrier Package with a low‐permeability vertical barrier inserted to represent the impediment of horizontal flow in faults characterized by sharp drops of the piezometric surface. Cavities can occur parallel to the strike of normal faults generating channels for the groundwater. In this case, flow models need to account for turbulence using a conduit network approach. Channels need to be embedded in an equivalent porous medium due to cavities a few centimeters large, which are present in carbonate aquifers even in areas characterized by low hydraulic gradients. Discrete fracture network modeling enables representation of individual rock discontinuities in three dimensions. This approach is used in non‐heavily karstified aquifers at industrial sites and was recently combined with the equivalent porous medium to simulate diffusivity in the matrix. Following this review, we recommend that the future research combines three practiced modeling approaches: equivalent porous medium, discrete fracture network, and conduit network, in order to capture structural and flow aspects in the modeling of groundwater in carbonate rocks.

• Torabi, Anita; Ellingsen, Tor Saltnes Skram; Johannessen, Magnus Ueland; Alaei, Behzad; Rotevatn, Atle & Chiarella, Domenico (2020). Fault zone architecture and its scaling laws: Where does the damage zone start and stop? Geological Society Special Publication. ISSN 0305-8719. 496, p. 99–124. doi: 10.1144/SP496-2018-151. Full text in Research Archive
• Lepillier, Baptiste; Bruna, Pierre-Olivier; Bruhn, David; Bastesen, Eivind; Daniilidis, Alexandros & Garcia, Óscar [Show all 8 contributors for this article] (2020). From outcrop scanlines to discrete fracture networks, an integrative workflow. Journal of Structural Geology. ISSN 0191-8141. 133, p. 1–16. doi: 10.1016/j.jsg.2020.103992. Full text in Research Archive Show summary

  Understanding fractures and fracture networks is essential for the investigation and use of subsurface reservoirs. The aim is to predict the fractures and the fracture network when there is no direct access to subsurface images available. This article presents a universal workflow to numerically compute a discrete fracture network by combining the 1D scanline survey method, processed with the newly written SkaPy script, together with the multiple point statistic method (MPS). This workflow is applied to a potential geothermal site in Mexico called Acoculco. We use Las Minas outcrops and quarries as surface analogues for the Acoculco reservoir, as Las Minas and Acoculco are both formed by the influence of a plutonic intrusion into the Jurassic–Cretaceous carbonate sequence of the Sierra Madre Oriental in the Trans-Mexican volcanic belt (TMVB). The intrusion is associated with contact metamorphism and metasomatic phenomena, providing the basis for the mining activities at Las Minas. The results obtained using this workflow demonstrate the feasibility of the approach, which presents a solution combining the efficiency of data processing and an interpretation-driven approach to build realistic discrete fracture networks. This workflow can be used in the process of estimating the permeability of a fracture controlled reservoir, with using only scanline surveys data as input. This is essential in the process of evaluating the feasibility to develop an enhanced geothermal system.

• Torabi, Anita; Jiménez-Millán, Juan; Jiménez-Espinosa, Rosario; García-Tortosa, Fransisco Juan & Ellingsen, Tor S.S. (2020). Effect of Mineral Processes and Deformation on the Petrophysical Properties of Soft Rocks during Active Faulting. Minerals. 10(5). doi: 10.3390/min10050444. Full text in Research Archive Show summary

  We have studied damage zones of two active faults, Baza and Padul faults in Guadix-Baza and Granada basins, respectively, in South Spain. Mineral and microstructural characterization by X-ray diffraction and field emission electron microscopy studies have been combined with structural fieldwork and in situ measurements of rock properties (permeability and Young’s modulus) to find out the relation between deformation behavior, mineral processes, and changes in the soft rock and sediment properties produced by fluid flow during seismic cycles. Our results show that microsealing produced by precipitation of dolomite and aragonite along fractures in the damage zone of Baza Fault reduces the permeability and increases the Young’s modulus. In addition, deformation bands formed in sediments richer in detrital silicates involved cataclasis as deformation mechanism, which hamper permeability of the sediments. In the Granada Basin, the calcarenitic rocks rich in calcite and clays in the damage zone of faults associated to the Padul Fault are characterized by the presence of stylolites without any carbonate cement. On the other hand, marly lithofacies affected by faults are characterized by the presence of disaggregation bands that involve cracking and granular flow, as well as clay smear. The presence of stylolites and deformation bands in these rocks reduces permeability.

• Torabi, Anita; Johannessen, Magnus Ueland & Ellingsen, Tor Saltnes Skram (2019). Fault core thickness: Insights from siliciclastic and carbonate rocks. Geofluids. ISSN 1468-8115. 2019. doi: 10.1155/2019/2918673. Full text in Research Archive Show summary

  Fault core accommodates intense deformation in the form of slip surfaces and fault rocks such as fault gouge, cataclasite, breccia, lenses, shale smear, and diagenetic features. The complexity and variation in fault core geometry and thickness affect fluid flow both along and across the fault. In this study, we have investigated a total of 99 faults in siliciclastic and carbonate rocks. This has resulted in two large datasets that include 871 fault core thickness measurements in siliciclastic rocks and 693 measurements in carbonates, conducted at regular intervals along fault elevations (fault height) on the outcrop or photos of the outcrop. Many of these measurements have been analyzed with respect to fault displacement measurements in order to study the relationship between displacement and fault core thickness and to further uncover the fault growth process. We found that the fault type and geometry, displacement, type of fault rocks, lithology, and competency contrasts between faulted layers lead to significant variations in the fault core internal structure and thickness. Analysis of average values of fault core thickness-displacement data of this study and of previously published studies shows that the core thickness-displacement relationship follows an overall power law, in which its exponent and intercept change depending on the lithology of the faulted rocks. In general, small faults in carbonate and siliciclastic rocks ( m) show comparable ratios, with a slightly higher ratio in carbonate rocks. The outcomes of this study contribute to the understanding of the fault core internal structure and variation in fault core thickness as a result of the interplay between fault displacement and host rock in different lithologies. These outcomes have significant implication for characterizing the sealing and conductivity potential of faulted rocks, which is relevant to different applications such as petroleum exploration and development of existing fields, hydrogeology, geothermal energy storage and extraction, and CO2 sequestration.

• Torabi, Anita; Alaei, Behzad & Libak, Audun (2019). Fault architecture, an integrated study. EarthDoc. p. 1–5. doi: 10.3997/2214-4609.201902315. Full text in Research Archive
• Torabi, Anita; Alaei, Behzad & Libak, Audun (2019). Normal fault 3D geometry and displacement revisited: Insights from faults in the Norwegian Barents Sea. Marine and Petroleum Geology. ISSN 0264-8172. 99, p. 135–155. doi: 10.1016/j.marpetgeo.2018.09.032. Full text in Research Archive
• Kolyukhin, Dmitriy; Torabi, Anita; Libak, Audun; Alaei, Behzad & Khachkova, Tatiana (2018). Statistical analysis of displacement and length relation for normal faults in the barents sea. Geosciences. 8(11), p. 1–10. doi: 10.3390/geosciences8110421. Full text in Research Archive
• Torabi, Anita; Alaei, Behzad & Ellingsen, TTS (2018). Faults and fractures in basement rocks, their architecture, petrophysical and mechanical properties. Journal of Structural Geology. ISSN 0191-8141. 117, p. 256–263. doi: 10.1016/j.jsg.2018.07.001. Full text in Research Archive
• Libak, Audun; Alaei, Behzad & Torabi, Anita (2017). Fault visualization and identification in fault seismic attribute volumes: Implications for fault geometric characterization. Interpretation. ISSN 2324-8858. 5(2), p. B1–B16. doi: 10.1190/INT-2016-0152.1. Full text in Research Archive
• Alaei, Behzad & Torabi, Anita (2017). Seismic imaging of fault damaged zone and its scaling relation with displacement. Interpretation. ISSN 2324-8858. 5(4), p. SP83–SP93. doi: 10.1190/int-2016-0230.1. Full text in Research Archive
• Rotevatn, Atle; Fossmark, Heidi Synnøve Solli; Bastesen, Eivind; Thorsheim, Elin & Torabi, Anita (2016). Do deformation bands matter for flow? Insights from permeability measurements and flow simulations in porous carbonate rocks. Petroleum Geoscience. ISSN 1354-0793. 23(1), p. 104–119. doi: 10.1144/petgeo2016-038. Full text in Research Archive Show summary

  We investigate the permeability and flow effects of deformation bands in porous granular carbonate rocks in Malta and use results from flow simulations to discuss the practical implications of deformation bands in carbonate and siliciclastic reservoirs rocks in general. Image- and laboratory-based analyses of deformation bands show permeabilities that are 1 – 2 orders of magnitude lower than the adjacent host rocks. Small-scale outcrop-based flow models (1 × 1 m) focus on the effect of deformation band on flow at the scale of individual bands. Two-phase flow simulations (water displacing oil) show that at the local scale a decrease in deformation band permeability led to increasing flow complexity, reduced and irregular waterfront propagation and reduction in sweep efficiency. A reduction in host rock permeability is associated with increased sensitivity to deformation bands. In low-permeable host rocks, a single magnitude-order reduction of deformation band permeability significantly delays flow, whereas in higher-permeable host rocks the effect is less pronounced. Hence, in some cases, deformation bands may represent a significant impediment to flow already when they are only 1 – 2 orders of magnitude less permeable than host rock. Consequently, deformation bands may have greater practical implications than previously thought, particularly in reservoir rocks with moderate to low host rock permeability.

• Rotevatn, Atle; Thorsheim, Elin; Bastesen, Eivind; Fossmark, Heidi Synnøve Solli; Torabi, Anita & Sælen, Gunnar (2016). Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes. Journal of Structural Geology. ISSN 0191-8141. 90, p. 27–47. doi: 10.1016/j.jsg.2016.07.003. Full text in Research Archive Show summary

  Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominating SCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved. We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.

• Torabi, Anita; Alaei, Behzad; Kolyukhin, Dmitriy; Libak, Audun; Gabrielsen, Roy Helge & Braathen, Alvar (2016). Fault geometric and seismic attributes; An integrated study with focus on the Barents Sea. First Break. ISSN 0263-5046. 34(5), p. 51–58. Full text in Research Archive
• Torabi, Anita; Alaei, Behzad & Kolyukhin, Dmitriy (2016). Analysis of fault scaling relations using fault seismic attributes. Geophysical Prospecting. ISSN 0016-8025. doi: 10.1111/1365-2478.12440. Full text in Research Archive
• Torabi, Anita; Alaei, Behzad; Kolyukhin, Dmitriy; Libak, Audun; Gabrielsen, Roy Helge & Braathen, Alvar (2016). Fault geometry and seismic attributes; an integrated study with focus on the Barents Sea. First Break. ISSN 0263-5046. 34(5), p. 51–58. Full text in Research Archive
• Skurtveit, Elin; Torabi, Anita; Alikarami, Reza & Braathen, Alvar (2015). Fault baffle to conduit developments: reactivation and calcite cementation of deformation band fault in aeolian sandstone. Petroleum Geoscience. ISSN 1354-0793. 21(1), p. 3–16. doi: 10.1144/petgeo2014-031. Full text in Research Archive
• Torabi, Anita; Gabrielsen, Roy; Fossen, Haakon; Ringrose, Philip; Skurtveit, Elin & Ando, Edward [Show all 15 contributors for this article] (2015). Strain localization in sandstone and its implications for CO2 storage. First Break. ISSN 0263-5046. 33(7), p. 81–92. Full text in Research Archive Show summary

  Geological storage of CO2 is a key technical solution to the climate-energy challenge, but it has a number of technological constraints (Baines and Worden 2004; Halland et al., 2011), broadly under the themes of assuring adequate storage capacity and long-term storage integrity. A suitable CO2-storage reservoir should consist of rock formations with sufficient porosity, permeability and connectivity in order to provide an adequate storage volume. The role of faults and their associated deformation structures (such as deformation bands and fractures) in controlling both storage capacity and long-term storage integrity is thus a key factor in achieving globally significant CO2 storage (Figure 1). Although some sedimentary basins on the Norwegian continental shelf already harbour operational CO2- injection and storage projects such as Sleipner (Zweigel et al., 2004) and Snøhvit (Hansen et al., 2013), our understanding of reservoir fluid communication due to compartmentalization is far from complete and will be important for further use of the offshore basins for CO2 storage. In addition to the inherited structural features, elevated injection pressures may cause hydraulic fractures or stimulate fault reactivation which both point to the need to characterize the geomechanical response of the rock system to CO2 injection (Rutqvist, 2012; Iding and Ringrose, 2010). In the present work, we investigate the effects of faults and their related structures on the geomechanical and petrophysical properties of sandstone reservoirs. Important components of fault systems include fractures and deformation bands in the damage zone and fault core (Caine et al., 1996; Shipton and Cowie, 2003; Fossen et al., 2007). Fault systems may enhance or suppress fluid communication, which in turn may affect the storage capacity and conductivity of the candidate reservoirs (Figure 1). As a case study, a reservoir model of the Tubåen Formation at the Snøhvit CO2 injection site in the Barents Sea (Grude et al., 2013; Hansen et al., 2013) was investigated using 4D seismic data and fault attribute analysis. The characteristics of deformation structures (e.g. sub-seismic faults, deformation bands and fractures) were investigated by field studies of outcrop analogues and by triaxial laboratory experiments to provide a basis for numerical modelling. Fault architecture within reactivated fault systems was studied by the use of analogue modelling. Key questions addressed in the work include: a) Where and when might strain localize in the reservoir? b) How does rock strain influence fluid communication? c) How might structural architecture affect CO2 storage effectiveness?

• Torabi, Anita; Aydin, Atilla; Cilona, Antonino; Jarstø, Benedikte E. & Deng, Shang (2015). The dynamics and interaction of compaction bands in Valley of Fire State Park, Nevada (USA): Implications for their growth, evolution, and geostatistical property. Tectonophysics. ISSN 0040-1951. 657, p. 113–128. doi: 10.1016/j.tecto.2015.06.029. Full text in Research Archive
• Rohmer, Jeremy; Nguyen, T.K. & Torabi, Anita (2015). Off-fault shear failure potential enhanced by high-stiff/low-permeable damage zone during fluid injection in porous reservoirs. Geophysical Journal International. ISSN 0956-540X. 202(1580), p. 1566–1566. doi: 10.1093/gji/ggv225. Full text in Research Archive
• Alikarami, Reza & Torabi, Anita (2015). Micro-texture and petrophysical properties of dilation and compaction shear bands in sand. Geomechanics for Energy and the Environment. ISSN 2352-3808. 3, p. 1–10. doi: 10.1016/j.gete.2015.06.001. Full text in Research Archive
• Denglin, Han; Man, Li; Zhong, Li & Torabi, Anita (2015). Sealing features of fluid-rock system and its control on acidic dissolution in cretaceous sandstone reservoirs, Kuqa Subbasin. Acta Geologica Sinica. ISSN 1000-9515. 89(4), p. 1296–1306. doi: 10.1111/1755-6724.12529. Full text in Research Archive
• Alikarami, Reza; Andò, Edward; Gkiousas-Kapnisis, Marius; Torabi, Anita & Viggiani, Gioacchino (2014). Strain localisation and grain breakage in sand under shearing at high mean stress: insights from in situ X-ray tomography. Acta Geotechnica. ISSN 1861-1125. 10(1), p. 15–30. doi: 10.1007/s11440-014-0364-6. Full text in Research Archive
• Torabi, Anita & Zarifi, Zoya (2014). Energy release rate of propagating deformation bands and their hosted cracks. International Journal of Rock Mechanics And Mining Sciences. ISSN 1365-1609. 67, p. 184–190. doi: 10.1016/j.ijrmms.2013.10.007. Full text in Research Archive
• Skurtveit, Elin; Ballas, G.; Fossen, Haakon; Torabi, Anita; Soliva, Roger & Peyret, M. (2014). Sand textural control on shear-enhanced compaction bands in poorly-lithified sandstone. Journal of geological resource and engineering. ISSN 2328-2193. 2(2). doi: 10.17265/2328-2193/2014.02.007. Full text in Research Archive Show summary

  Sand textural control on SECB (shear-enhanced compaction band) formation is analyzed combining field observations, detailed material characterization and mechanical testing for poorly lithified sandstone units in Provence (France). Field observations show that SECBs are densely distributed in a coarse-grained unit with moderate porosity (27%), whereas few SECBs are developed within the overlying fine-grained, high-porosity (39%) unit. Results from textural characterization show that the main difference between the two sand units is grain size and sorting, whereas they are similar with respect to composition and grain angularity. Packing density is introduced as an important parameter for comparing the compaction properties independent of the textural variations between the two units. Compaction experiments show a slightly faster compaction of the coarse-grained sand as compared to the fine-grained sand, and more pronounced grain crushing is observed in the coarse-grained unit. The results indicate that the preferential localization of SECBs to the coarse-grained unit is controlled by a slightly denser packing of the coarse-grained material at the time of band formation together with higher stress concentrations on grain contacts. Hence, this study emphasizes that porosity alone is an insufficient parameter for predicting deformation band evolution in sand (stone).

• Torabi, Anita (2014). Cataclastic bands in immature and poorly lithified sandstone, examples from Corsica, France. Tectonophysics. ISSN 0040-1951. 630(1), p. 91–102. doi: 10.1016/j.tecto.2014.05.014. Full text in Research Archive
• Skurtveit, Elin; Torabi, Anita; Gabrielsen, Roy H. & Zoback, Mark D. (2013). Experimental investigation of deformation mechanisms during shear-enhanced compaction in poorly lithified sandstone and sand. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 118(8), p. 4083–4100. doi: 10.1002/jgrb.50342. Full text in Research Archive Show summary

  Shear-enhanced compaction in shallow sandstone reservoirs has been investigated in laboratory experiments using high-pressure triaxial testing of poorly lithified sandstone and sand. We have studied the deformation mechanism involved during shear-enhanced compaction and controlling parameters for yield stress at varying confining pressures for sandstone/sand with different grain sizes, porosities, and packing. Experimental testing provides insights into the deformation mechanism during hydrostatic and axial compression of coarse- and fine-grained sands with different packing including (1) natural coarse-grained sandstone, (2) densely packed fine-grained sand, and (3) loosely packed fine-grained sand. Monitoring of deformation and ultrasonic velocity during deformation indicates porosity loss, compaction, and strain hardening for most of the samples. Visualization of deformation using pretest and posttest X-ray imaging and thin sections demonstrates localized deformation fabrics and grain damage. The results show grain rearrangement as the controlling deformation mechanism for material at low stress and high porosity, whereas for lower porosity and higher stress, grain fracturing controlled the deformation. The most pronounced localization of deformation was observed for the coarse-grained, low-porosity material. A Cam-Clay cap model was used to describe the porosity loss during compaction and shear-enhanced compaction, demonstrating large inelastic compaction with increasing confining pressure. Yield stress and end caps for poorly lithified sandstone are observed for various porosities and stress conditions and found to be lower than predicted using empirical relationships for sandstone.

• Kolyukhin, Dmitriy & Torabi, Anita (2013). Power-law testing for fault attributes distributions. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. 170(12), p. 2173–2183. doi: 10.1007/s00024-013-0644-3. Full text in Research Archive Show summary

  Abstract This paper is devoted to statistical analysis of faults’ attributes. The distributions of lengths, widths of damage zones, displacements and thicknesses of fault cores are studied. Truncated power-law (TPL) is considered in comparison with commonly used simple power-law (PL) (or Pareto) distribution. The maximal likelihood and the confidence interval of the exponent for both PL and TPL are estimated by appropriate statistical methods. The Kolmogorov–Smirnov (KS) test and the likelihood ratio test with alternative non-nested hypothesis for exponential distribution are used to verify the statistical approximation. Furthermore, the advantage of TPL is proved by Bayesian information criterion. Our results suggest that a TPL is more suitable for describing fault attributes, and that its condition is satisfied for a wide range of fault scales. We propose that using truncated power laws in general might eliminate or relax the bias related to sampling strategy and the resolution of measurements (such as censoring, truncation, and cut effect) and; therefore, the most reliable range of data can be considered for the statistical approximation of fault attributes.

• Torabi, Anita; Fossen, Haakon & Braathen, Alvar (2013). Insight into petrophysical properties of deformed sandstone reservoirs. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 97(4), p. 619–637. doi: 10.1306/10031212040. Full text in Research Archive
• Torabi, Anita & Skurtveit, Elin (2013). Effect of initial grain size and packing on the evolution of elastic properties of poorly lithified sandstones. In Pyrak-Nolte, L.J. (Eds.), 47th US Rock Mechanics / Geomechanics Symposium 2013. Proceedings of a meeting held 23-26 June 2013, San Francisco, California, USA. Curran Associates, Inc.. ISSN 9781629931180. p. 245–251. Full text in Research Archive
• Alikarami, Reza; Torabi, Anita; Kolyukhin, Dmitriy & Skurtveit, Elin (2013). Geostatistical relationships between mechanical and petrophysical properties of deformed sandstone. International Journal of Rock Mechanics And Mining Sciences. ISSN 1365-1609. 63, p. 27–38. doi: 10.1016/j.ijrmms.2013.06.002. Full text in Research Archive
• Kolyukhin, Dmitriy & Torabi, Anita (2012). Statistical analysis of the relationships between faults attributes. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 117. doi: 10.1029/2011JB008880. Full text in Research Archive
• Fossen, Haakon; Schultz, Richard A. & Torabi, Anita (2011). Conditions and implications for compaction band formation in the Navajo Sandstone, Utah. Journal of Structural Geology. ISSN 0191-8141. 33(10), p. 1477–1490. doi: 10.1016/j.jsg.2011.08.001. Full text in Research Archive
• Torabi, Anita & Berg, Silje Støren (2011). Scaling of fault attributes: A review. Marine and Petroleum Geology. ISSN 0264-8172. 28(8), p. 1444–1460. doi: 10.1016/j.marpetgeo.2011.04.003. Full text in Research Archive
• Torabi, Anita & Fossen, Haakon (2009). Spatial variation of microstructure and petrophysical properties along deformation bands in reservoir sandstones. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 93(7), p. 919–938. doi: 10.1306/03270908161. Full text in Research Archive
• Torabi, Anita & Fossen, Haakon (2009). Variation of microstructure and petrophysical properties along deformation bands. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 93, p. 919–938. doi: 10.1306/03270908161. Full text in Research Archive
• Torabi, Anita & Fossen, Haakon (2009). Spatial variation of microstructure and petrophysical properties along deformation bands in reservoir sandstones. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 93(7), p. 919–938. doi: 10.1306/03270908161. Full text in Research Archive
• Rotevatn, Atle; Torabi, Anita; Fossen, Haakon & Braathen, Alvar (2008). Slipped deformation bands: A new type of cataclastic deformation bands in Western Sinai, Suez rift, Egypt. Journal of Structural Geology. ISSN 0191-8141. 30(11), p. 1317–1331. doi: 10.1016/j.jsg.2008.06.010. Full text in Research Archive
• Torabi, Anita; Fossen, Haakon & Alaei, Behzad (2008). Application of spatial correlation functions in permeability estimation of deformation bands in porous rocks. Journal of Geophysical Research (JGR). ISSN 0148-0227. 113. doi: 10.1029/2007JB005455. Full text in Research Archive
• Torabi, Anita; Braathen, Alvar; Cuisiat, Fabrice & Fossen, Haakon (2007). Shear zones in porous sand: Insights from ring-shear experiments and naturally deformed sandstones. Tectonophysics. ISSN 0040-1951. 437(1-4), p. 37–50. doi: 10.1016/j.tecto.2007.02.018. Full text in Research Archive

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• Munoz, Jhon-Meyer; Torabi, Anita; Basa, Abhisek; Hansen, Torsten Hundebøl & Skurtveit, Elin (2026). Fault-core in overburden section: geomechanical and geo chemical characterisation of the Baza fault core, southern Spain. In Ziegler, Martin; Nicol, Romain; Jaeggi, David & Nussbaum, Christophe (Ed.), Caprock Integrity & Gas Storage Symposium 2026. Swiss Federal Office of Topography. p. 41–45. doi: https:/www.swisstopo.admin.ch/dam/en/sd-web/jwHxgZfGm5AB/Conference%20Proceedings%20CIGSS%202026.pdf. Full text in Research Archive
• Ghione, Federica; Molina-Palacios, Sergio; Torabi, Anita & Oye, Volker (2024). Comprehensive Seismic Risk Assessment for Oslo (Norway): Integrating Deterministic and Probabilistic Approaches for Community-Specific Insights. Full text in Research Archive
• Dombrovski, Elisaveta; Mondol, Nazmul Haque; Bohloli, Bahman; Gaina, Carmen & Torabi, Anita (2021). Monitoring ground surface and seafloor deformation caused by subsurface fluid injection. Full text in Research Archive
• Dombrovski, Elisaveta; Mondol, Nazmul Haque; Bohloli, Bahman & Torabi, Anita (2021). Applying machine learning on InSAR data for carbon sequestration site monitoring. Full text in Research Archive
• Skurtveit, Elin; Bjørnarå, Tore Ingvald; Bohloli, Bahman; Soldal, Magnus; Eidsvig, Unni & Gasda, Sarah [Show all 9 contributors for this article] (2020). Dynamic changes in fault permeability – How can experimental work provide support for fault seal integrity? Full text in Research Archive
• Skurtveit, Elin; Bjørnarå, Tore Ingvald; Bohloli, Bahman; Soldal, Magnus; Eidsvig, Unni & Gasda, Sarah [Show all 10 contributors for this article] (2020). Dynamic changes in fault permeability How can experimental work provide support for fault seal integrity? Full text in Research Archive
• Buckley, Simon John & Torabi, Anita (2018). Uni Research CIPR Geoscience and Virtual Outcrop Geology. Full text in Research Archive
• Midtkandal, Ivar; Sundal, Anja; Braathen, Alvar; Petrie, Elizabeth; Evans, James R. & Zuchuat, Valentin [Show all 10 contributors for this article] (2018). Project summary: CO2 seal bypass - a multidisciplinary approach to CO2 migration and storage. Full text in Research Archive
• Dmitriy, Kolyukhin; Torabi, Anita & I., Silvestrov (2015). Fault attributes and relations between them, taking into account the sampling bias. Full text in Research Archive
• Behzad, Alaei & Torabi, Anita (2015). 3D fault plane geometry and fault scaling studies using seismic attributes. Full text in Research Archive
• Torabi, Anita; Jarstø, Benedikte E.; Cilona, Antonino & Deng, Shang (2015). Geometry, microstructure and petrophysical properties of compaction and shear bands at Silica Dome, Valley of Fire State Park, Nevada, USA. Full text in Research Archive
• Kolyukhin, Dmitriy; Torabi, Anita & Tveranger, Jan (2014). Statistical analysis of fault attributes and relation between them; Simulation of fault zone structures. Full text in Research Archive
• Skurtveit, Elin; Torabi, Anita; Braathen, Alvar & Alikarami, Reza (2014). Fault Zone Development with Temporal Impact on Fluid Flow - Example from Navajo Sandstone, Utah. Full text in Research Archive
• Torabi, Anita & Berg, Silje S. (2010). Scaling of fault attributes. Full text in Research Archive
• Torabi, Anita & Fossen, Haakon (2009). Anisotropy in the petrophysical properties of deformation bands. Full text in Research Archive
• Fossen, Haakon; Schultz, Richard; Torabi, Anita & Tveranger, Jan (2009). Petrophysically selective compaction bands in Navajo Sandstone. Full text in Research Archive
• Torabi, Anita & Fossen, Haakon (2008). Variation of petrophysical properties along deformation bands and its implication in petroleum reservoirs. Full text in Research Archive
• Torabi, Anita; Fossen, Haakon & Alaei, Behzad (2007). Permeability estimation of deformed sandstone using image processing. Full text in Research Archive
• Torabi, Anita; Braathen, Alvar; Cuisiat, Fabrice; Skurtveit, Elin; Fossen, Haakon & Grande, Lars (2006). Shear zones in porous sand from high stress ring-shear experiments. Full text in Research Archive
• Ahmed, Shajahat; Torabi, Anita & Braathen, Alvar (2020). Structural analysis of Horda Platform and Stord Basin in the Norwegian North Sea using Machine Learning methods. Universitetet i Oslo. Full text in Research Archive Show summary

  The detection of geological structures in seismic data is of great importance for applications concerning storage and extraction of resources from the subsurface reservoirs, such as oil and gas exploration and production, CO2 and waste storage, geothermal resources. However, interpretation of seismic data is a time-consuming task. In this thesis, we present an automated approach using light U-net, which is a 3D convolutional neural networks (CNNs) algorithm to identify geological structures such as faults in 3D seismic cubes. Delineating faults from seismic images is a key step for seismic structural interpretation, characterization of reservoirs and well positioning. In conventional methods for seismic interpretation, faults are picked as discontinuities along seismic reflectors and/or are identified by measuring attributes that estimate discontinuities (e.g. coherence attributes) in seismic data. In this study, we perform fault detection as a binary image segmentation problem through labeling a 3D seismic image with one for fault and zero for no-fault. We have implemented an effective image-to-image fault segmentation using a supervised, fully convolutional neural network. We automatically generate various amounts of 3D seismic images and corresponding binary fault labeling images to train the network, which is shown to be sufficient to train a thriving network of fault segments. Since a binary fault image is highly imbalanced between zero (no-fault) and one (fault), we use a class-balanced binary cross-entropy loss function to change the imbalance so that the network is not trained or gathered to predict only zeros (no-fault). After training several 3D seismic data sets, the network automatically learns to calculate the rich and correct features that are critical for fault detection. Our results from using this approach on multiple 3D seismic surveys from Horda Platfrom and Stord Basin indicate that the neural network can predict faults from 3D seismic images much more accurately and efficiently than conventional methods. Further, we analyzed frequency of minor faults in 3D around two major faults in Horda Platform, Vette and Øygarden faults. Using this analysis, we investigated how damage zone architecture of these two major faults changes along different scanlines with respect to time and different inlines. Our results show that more minor faults are observed around the Vette Fault, indicating a larger damage zone around this fault. This damage zone is expected to extend southward as minor faults are distributed over a wide region on 1300-1500 inlines. Whereas the damage zone around Øygarden Fault includes a few to no minor faults in seismic scale on most of the inlines.

• Torabi, Anita (2008). Deformation bands in porous sandstones, their microstructure and petrophysical properties. Universitetet i Bergen. ISSN 9788230805282. Full text in Research Archive Show summary

  Deformation bands are commonly thin tabular zones of crushed or reorganized grains that form in highly porous rocks and sediments. Unlike a fault, typically the slip is negligible in deformation bands. In this dissertation the microstructure and petrophysical properties of deformation bands have been investigated through microscopy and numerical analysis of experimental and natural examples. The experimental work consists of a series of ring-shear experiments performed on porous sand at 5 and 20 MPa normal stresses and followed by microscopic examination of thin sections from the sheared samples. The results of the ring-shear experiments and comparison of them to natural deformation bands reveals that burial depth (level of normal stress in the experiments) and the amount of shear displacement during deformation are the two significant factors influencing the mode in which grains break and the type of shear zone that forms. Two end-member types of experimental shear zones were identified: (a) Shear zones with diffuse boundaries, which formed at low levels of normal stress and/or shear displacement; and (b) Shear zones with sharp boundaries, which formed at higher levels of normal stress and/or shear displacement. Our interpretation is that with increasing burial depth (approximately more than one kilometer, simulated in the experiments by higher levels of normal stress), the predominant mode of grain fracturing changes from flaking to splitting; which facilitates the formation of sharp-boundary shear zones. This change to grain splitting increases the power law dimension of the grain size distribution (D is about 1.5 in sharp boundary shear zones). Based on our observations, initial grain size has no influence in the deformation behavior of the sand at 5 MPa normal stresses. A new type of cataclastic deformation band is described through outcrop and microscopic studies; here termed a "slipped deformation band". Whereas previouslyreported cataclastic deformation bands are characterized by strain hardening, these new bands feature a central slip surface, which indicates late strain softening. They lack the characteristic compaction envelop, and are typified by higher porosity and lower permeability than previously-described cataclastic deformation bands. Intense background fracturing of the host rock and significant initial porosity are considered to be important in creating these newly-discovered deformation bands. In a related study, we investigate, for millimeter- wide deformation bands, the scale limitation inherent in laboratory measurements of porosity and permeability. The scale limitations imposed by the deformation band relative to the physical sample size motivated us to develop a new method for determining porosity and permeability based on image processing. While plug measurements measure the effective permeability across a 25.4 mm (1 inch) long sample, which includes both host rock and deformation band, the method presented here provides a means to estimate porosity and permeability of deformation band on microscale. This method utilizes low-order (one- and twoorders) spatial correlation functions to analyze high-resolution, high-magnification backscatter images, to estimate the porosity and specific surface area of the pore-grain interface in the deformed sandstones. Further, this work demonstrates the use of a modified version of the Kozeny-Carmen relation to calculate permeability by using porosity and specific surface area obtained through the image processing. The result shows that permeability difference between the band and the host rock is up to four orders of magnitude. Moreover, the porosities and permeabilities estimated from image processing are lower than those obtained from their plug measurements; hence the traditional laboratory measurements have been overestimating permeability because of the previously-unrecognized scale problem. In addition, the image processing results clearly show that, as a result of microstructural variation, both porosity and permeability vary along the length of individual deformation bands, with permeability variations of up to two orders of magnitude. Such petrophysical variations are found in several types of deformation bands (disaggregation, cataclastic and dissolution bands), but the range depends on the deformation mechanisms, in particular on the degree of (i) cataclasis, (ii) dissolution in cataclastic and dissolution bands, and (iii) on the phyllosilicate content in disaggregation bands. This microscopic anisotropy in the petrophysical properties of deformation bands opens up a new and fruitful area for further research. Our results show that for phyllosilicate bands the band thickness is related to the phyllosilicate content, whereas for cataclastic bands no apparent correlation was found between thickness and intensity of cataclasis.

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