Articles | Volume 13, issue 5
https://doi.org/10.5194/se-13-901-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-13-901-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
16 May 2022
Research article |
| 16 May 2022
| 16 May 2022
Failure mode transition in Opalinus Clay: a hydro-mechanical and microstructural perspective
Lisa Winhausen
CORRESPONDING AUTHOR
Department of Engineering Geology and Hydrogeology, RWTH Aachen
University, Lochnerstraße 4–20, 52064 Aachen, Germany
Kavan Khaledi
Department of Engineering Geology and Hydrogeology, RWTH Aachen
University, Lochnerstraße 4–20, 52064 Aachen, Germany
Mohammadreza Jalali
Department of Engineering Geology and Hydrogeology, RWTH Aachen
University, Lochnerstraße 4–20, 52064 Aachen, Germany
Janos L. Urai
Institute of Tectonics and Geodynamics, RWTH Aachen University,
Lochnerstraße 4–20, 52064 Aachen, Germany
Florian Amann
Department of Engineering Geology and Hydrogeology, RWTH Aachen
University, Lochnerstraße 4–20, 52064 Aachen, Germany
Fraunhofer IEG, Fraunhofer Research Institution for Energy
Infrastructures and Geothermal Systems, Kockerellstraße 17, 52062
Aachen, Germany
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Lisa Winhausen, Mohammadreza Jalali, and Florian Amann
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Solid Earth, 12, 2109–2126, https://doi.org/10.5194/se-12-2109-2021, https://doi.org/10.5194/se-12-2109-2021, 2021
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An experimentally deformed sample of Opalinus Clay (OPA), which is being considered as host rock for nuclear waste in Switzerland, was studied by electron microscopy to image deformation microstructures. Deformation localised by forming micrometre-thick fractures. Deformation zones show dilatant micro-cracking, granular flow and bending grains, and pore collapse. Our model, with three different stages of damage accumulation, illustrates microstructural deformation in a compressed OPA sample.
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We detail the selection and characterization of a fault zone for earthquake experiments in the Fault Activation and Earthquake Ruptures (FEAR) project at the Bedretto Lab. FEAR, which studies earthquake processes, overcame data collection challenges near faults. The fault zone in Rotondo granite was selected based on geometry, monitorability, and hydro-mechanical properties. Remote sensing, borehole logging, and geological mapping were used to create a 3D model for precise monitoring.
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We analysed Zechstein salt with microscopes and observed specific microstructures that indicate much faster deformation in rock salt with fine halite grains when compared to salt with larger grains. This is important because people build large cavities in the subsurface salt for energy storage or want to deposit radioactive waste inside it. When engineers and scientists use grain-size data and equations that include this mechanism, it will help to make better predictions in geological models.
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Manuscript not accepted for further review
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Lisa Maria Ringel, Mohammadreza Jalali, and Peter Bayer
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Fractured rocks host a class of aquifers that serve as major freshwater resources worldwide. This work is dedicated to resolving the three-dimensional hydraulic and structural properties of fractured rock. For this purpose, hydraulic tomography experiments at the Grimsel Test Site in Switzerland are utilized, and the discrete fracture network is inverted. The comparison of the inversion results with independent findings from other studies demonstrates the validity of the approach.
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Understanding the mechanism of mechanical compaction is important. Previous studies on mechanical compaction were mostly done by performing experiments. Studies on natural rocks are rare due to compositional heterogeneity of the sedimentary succession with depth. Due to remarkable similarity in composition and grain size, the Sumatra subduction complex provides a unique opportunity to study the micromechanism of mechanical compaction on natural samples.
Manuel D. Menzel, Janos L. Urai, Estibalitz Ukar, Thierry Decrausaz, and Marguerite Godard
Solid Earth, 13, 1191–1218, https://doi.org/10.5194/se-13-1191-2022, https://doi.org/10.5194/se-13-1191-2022, 2022
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Mantle rocks can bind large quantities of carbon by reaction with CO2, but this capacity requires fluid pathways not to be clogged by carbonate. We studied mantle rocks from Oman to understand the mechanisms allowing their transformation into carbonate and quartz. Using advanced imaging techniques, we show that abundant veins were essential fluid pathways driving the reaction. Our results show that tectonic stress was important for fracture opening and a key ingredient for carbon fixation.
Xiaodong Ma, Marian Hertrich, Florian Amann, Kai Bröker, Nima Gholizadeh Doonechaly, Valentin Gischig, Rebecca Hochreutener, Philipp Kästli, Hannes Krietsch, Michèle Marti, Barbara Nägeli, Morteza Nejati, Anne Obermann, Katrin Plenkers, Antonio P. Rinaldi, Alexis Shakas, Linus Villiger, Quinn Wenning, Alba Zappone, Falko Bethmann, Raymi Castilla, Francisco Seberto, Peter Meier, Thomas Driesner, Simon Loew, Hansruedi Maurer, Martin O. Saar, Stefan Wiemer, and Domenico Giardini
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Ben Laurich, Jürgen Hesser, Sibylle Mayr, Lisa Winhausen, Amin Ghanizadeh, Antonia Nitsch, Julia Leuthold, Christian Weber, and Garri Gaus
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Hannes Krietsch, Valentin S. Gischig, Joseph Doetsch, Keith F. Evans, Linus Villiger, Mohammadreza Jalali, Benoît Valley, Simon Löw, and Florian Amann
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Hydraulic stimulation summarizes fracture initiation and reactivation due to high-pressure fluid injection. Several borehole intervals covering intact rock and pre-existing fractures were targets for high-pressure fluid injections within a decameter-scale, crystalline rock volume. The observed induced seismicity strongly depends on the target geology. In addition, the severity of the induced seismicity per experiment counter correlates with the observed transmissivity enhancement.
Heijn van Gent and Janos L. Urai
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Faults form due to stresses caused by crustal processes. As faults influence the stress field locally, fault interaction leads to local variations in the stress field, but this is difficult to observe directly.
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Nathan Dutler, Benoît Valley, Valentin Gischig, Linus Villiger, Hannes Krietsch, Joseph Doetsch, Bernard Brixel, Mohammadreza Jalali, and Florian Amann
Solid Earth, 10, 1877–1904, https://doi.org/10.5194/se-10-1877-2019, https://doi.org/10.5194/se-10-1877-2019, 2019
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In this study, we present seismo-hydromechanical results from six hydraulic fracturing experiments executed in the framework of the In-situ Stimulation and Circulation (ISC) project. The well-characterized and extensively monitored target rock allows for the study of (1) the response of the rock mass, (2) the injection and pore pressure response, and (3) the geometry of newly created fractures and their interaction with the natural fracture network.
Christopher Weismüller, Janos L. Urai, Michael Kettermann, Christoph von Hagke, and Klaus Reicherter
Solid Earth, 10, 1757–1784, https://doi.org/10.5194/se-10-1757-2019, https://doi.org/10.5194/se-10-1757-2019, 2019
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We use drones to study surface geometries of massively dilatant faults (MDFs) in Iceland, with apertures up to tens of meters at the surface. Based on throw, aperture and structures, we define three geometrically different endmembers of the surface expression of MDFs and show that they belong to one continuum. The transition between the endmembers is fluent and can change at one fault over short distances, implying less distinct control of deeper structures on surface geometries than expected.
Mark G. Rowan, Janos L. Urai, J. Carl Fiduk, and Peter A. Kukla
Solid Earth, 10, 987–1013, https://doi.org/10.5194/se-10-987-2019, https://doi.org/10.5194/se-10-987-2019, 2019
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Ancient evaporite sequences were deposited as interlayered rocksalt, other evaporites, and non-evaporite rocks that have enormous differences in strength. Whereas the ductile layers flow during deformation, strong layers are folded and/or torn apart, with the intrasalt deformation dependent on the mode and history of salt tectonics. This has important implications for accurately imaging and interpreting subsurface seismic data and for drilling wells through evaporite sequences.
Ismay Vénice Akker, Josef Kaufmann, Guillaume Desbois, Jop Klaver, Janos L. Urai, Alfons Berger, and Marco Herwegh
Solid Earth, 9, 1141–1156, https://doi.org/10.5194/se-9-1141-2018, https://doi.org/10.5194/se-9-1141-2018, 2018
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We studied porosity changes of slates from eastern Switzerland, which were deposited in an ocean in front of the emerging Alps during the Cenozoic. The Alpine collision between the European and African plates brought the rocks from this basin to today’s position in the Alps. From the basin to the surface, the porosity first decreased down to a small number of round cavities (<1 vol%) to microfractures, and once at the surface, the porosity increased again due to the formation of macro-fractures.
Florian Amann, Valentin Gischig, Keith Evans, Joseph Doetsch, Reza Jalali, Benoît Valley, Hannes Krietsch, Nathan Dutler, Linus Villiger, Bernard Brixel, Maria Klepikova, Anniina Kittilä, Claudio Madonna, Stefan Wiemer, Martin O. Saar, Simon Loew, Thomas Driesner, Hansruedi Maurer, and Domenico Giardini
Solid Earth, 9, 115–137, https://doi.org/10.5194/se-9-115-2018, https://doi.org/10.5194/se-9-115-2018, 2018
Simon Virgo, Christoph von Hagke, and Janos L. Urai
Solid Earth, 9, 91–113, https://doi.org/10.5194/se-9-91-2018, https://doi.org/10.5194/se-9-91-2018, 2018
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The marbles of the migmatitic dome on the island Naxos contain deformed layers of amphibolite with multiple phases of boudinage. The boudins formed by E–W shortening normal to the layers and layer parallel extension in various directions. We identified five different generations of boudins that show that E–W shortening is the prevalent deformation in these rocks during the peak metamorphosis and the following cooling, different from other parts of the island dominated by top-to-north shearing.
Valentin Samuel Gischig, Joseph Doetsch, Hansruedi Maurer, Hannes Krietsch, Florian Amann, Keith Frederick Evans, Morteza Nejati, Mohammadreza Jalali, Benoît Valley, Anne Christine Obermann, Stefan Wiemer, and Domenico Giardini
Solid Earth, 9, 39–61, https://doi.org/10.5194/se-9-39-2018, https://doi.org/10.5194/se-9-39-2018, 2018
Ben Laurich, Janos L. Urai, Christian Vollmer, and Christophe Nussbaum
Solid Earth, 9, 1–24, https://doi.org/10.5194/se-9-1-2018, https://doi.org/10.5194/se-9-1-2018, 2018
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In Switzerland, the Opalinus Clay (OPA) formation is favored to host a repository for nuclear waste. Thus, we must know its deformation behavior. In this study, we focused on the microstructure of gouge, a thin (< 2 cm), drastically strained clay layer at the so-called Main Fault in the Mont Terri rock laboratory. We suggest that in situ gouge deforms in a more viscous manner than undeformed OPA in laboratory conditions. Moreover, we speculate about the origin and evolution of the gouge layer.
Katrin M. Wild, Patric Walter, and Florian Amann
Solid Earth, 8, 351–360, https://doi.org/10.5194/se-8-351-2017, https://doi.org/10.5194/se-8-351-2017, 2017
Guillaume Desbois, Nadine Höhne, Janos L. Urai, Pierre Bésuelle, and Gioacchino Viggiani
Solid Earth, 8, 291–305, https://doi.org/10.5194/se-8-291-2017, https://doi.org/10.5194/se-8-291-2017, 2017
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This work integrates measurements of the mechanical and transport properties with microstructures to understand deformation mechanisms in cemented mudrock. Cataclastic mechanisms are dominant down to nanometre scale. At low strain the fabric contains recognizable open fractures, while at high strain the reworked clay gouge shows resealing of initial fracture porosity. In the future, it will provide a microphysical basis for constitutive models to improve their extrapolation for long timescales.
Ben Laurich, Janos L. Urai, and Christophe Nussbaum
Solid Earth, 8, 27–44, https://doi.org/10.5194/se-8-27-2017, https://doi.org/10.5194/se-8-27-2017, 2017
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Scaly clay is a well-known rock fabric that can develop in tectonic systems and that can alter the physical rock properties of a formation. However, the internal microstructure and evolution of this fabric remain poorly understood. We examined the scaly microstructure of progressively faulted Opalinus Clay using optical as well as scanning electron microscopy. We show that as little as 1 vol.% in scaly clay aggregates is strained and present an evolutionary model for this.
A. F. Raith, F. Strozyk, J. Visser, and J. L. Urai
Solid Earth, 7, 67–82, https://doi.org/10.5194/se-7-67-2016, https://doi.org/10.5194/se-7-67-2016, 2016
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3D seismic and well data were used to study the evolution of salt pillows with extreme mechanical stratification to gain a better understanding of layered evaporite deposits. During evaporation an active basement graben caused the local accumulation of thick K-Mg salts. The resulting structure after the following extensional and compressional salt flow was strongly influenced by folding of the ruptured ZIII-AC stringer, leading to thickening and internal deformation of the soft K-Mg salt layers.
Related subject area
Subject area: Tectonic plate interactions, magma genesis, and lithosphere deformation at all scales | Editorial team: Structural geology and tectonics, paleoseismology, rock physics, experimental deformation | Discipline: Mineral and rock physics
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Roberto Emanuele Rizzo, Damien Freitas, James Gilgannon, Sohan Seth, Ian B. Butler, Gina Elizabeth McGill, and Florian Fusseis
Solid Earth, 15, 493–512, https://doi.org/10.5194/se-15-493-2024, https://doi.org/10.5194/se-15-493-2024, 2024
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Here we introduce a new approach for analysing time-resolved 3D X-ray images tracking mineral changes in rocks. Using deep learning, we accurately identify and quantify the evolution of mineral components during reactions. The method demonstrates high precision in quantifying a metamorphic reaction, enabling accurate calculation of mineral growth rates and porosity changes. This showcases artificial intelligence's potential to enhance our understanding of Earth science processes.
Marco Fuchs, Anna Suzuki, Togo Hasumi, and Philipp Blum
Solid Earth, 15, 353–365, https://doi.org/10.5194/se-15-353-2024, https://doi.org/10.5194/se-15-353-2024, 2024
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In this study, the permeability of a natural fracture in sandstone is estimated based only on its geometry. For this purpose, the topological method of persistent homology is applied to three geometric data sets with different resolutions for the first time. The results of all data sets compare well with conventional experimental and numerical methods. Since the analysis takes less time to the same amount of time, it seems to be a good alternative to conventional methods.
Jianwei Ren, Lei Song, Qirui Wang, Haipeng Li, Junqi Fan, Jianhua Yue, and Honglei Shen
Solid Earth, 14, 261–270, https://doi.org/10.5194/se-14-261-2023, https://doi.org/10.5194/se-14-261-2023, 2023
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A THMC multi-field rock resistivity test system is developed, which has the functions of rock triaxial and resistivity testing under the conditions of high and low temperature, high pressure, and high salinity water seepage. A sealing method to prevent the formation of a water film on the side of the specimen is proposed based on the characteristics of the device. The device is suitable for studying the relationship between rock mechanical properties and resistivity in complex environments.
Lauren Kedar, Clare E. Bond, and David K. Muirhead
Solid Earth, 13, 1495–1511, https://doi.org/10.5194/se-13-1495-2022, https://doi.org/10.5194/se-13-1495-2022, 2022
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Raman spectroscopy of carbon-bearing rocks is often used to calculate peak temperatures and therefore burial history. However, strain is known to affect Raman spectral parameters. We investigate a series of deformed rocks that have been subjected to varying degrees of strain and find that there is a consistent change in some parameters in the most strained rocks, while other parameters are not affected by strain. We apply temperature calculations and find that strain affects them differently.
Zhilin Ye, Dawei Fan, Bo Li, Qizhe Tang, Jingui Xu, Dongzhou Zhang, and Wenge Zhou
Solid Earth, 13, 745–759, https://doi.org/10.5194/se-13-745-2022, https://doi.org/10.5194/se-13-745-2022, 2022
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Eclogite is a major factor in the initiation of delamination during orogenic collision. According to the equations of state of main minerals of eclogite under high temperature and high pressure, the densities of eclogite along two types of delamination in Tibet are provided. The effects of eclogite on the delamination process are discussed in detail. A high abundance of garnet, a high Fe content, and a high degree of eclogitization are more conducive to instigating the delamination.
Tiange Xing, Hamed O. Ghaffari, Ulrich Mok, and Matej Pec
Solid Earth, 13, 137–160, https://doi.org/10.5194/se-13-137-2022, https://doi.org/10.5194/se-13-137-2022, 2022
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Geological carbon sequestration using basalts provides a solution to mitigate the high CO2 concentration in the atmosphere. Due to the long timespan of the GCS, it is important to understand the long-term deformation of the reservoir rock. Here, we studied the creep of basalt with fluid presence. Our results show presence of fluid weakens the rock and promotes creep, while the composition only has a secondary effect and demonstrate that the governing creep mechanism is subcritical microcracking.
Lisa Winhausen, Jop Klaver, Joyce Schmatz, Guillaume Desbois, Janos L. Urai, Florian Amann, and Christophe Nussbaum
Solid Earth, 12, 2109–2126, https://doi.org/10.5194/se-12-2109-2021, https://doi.org/10.5194/se-12-2109-2021, 2021
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An experimentally deformed sample of Opalinus Clay (OPA), which is being considered as host rock for nuclear waste in Switzerland, was studied by electron microscopy to image deformation microstructures. Deformation localised by forming micrometre-thick fractures. Deformation zones show dilatant micro-cracking, granular flow and bending grains, and pore collapse. Our model, with three different stages of damage accumulation, illustrates microstructural deformation in a compressed OPA sample.
Michael J. Schmidtke, Ruth Keppler, Jacek Kossak-Glowczewski, Nikolaus Froitzheim, and Michael Stipp
Solid Earth, 12, 1801–1828, https://doi.org/10.5194/se-12-1801-2021, https://doi.org/10.5194/se-12-1801-2021, 2021
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Properties of deformed rocks are frequently anisotropic. One of these properties is the travel time of a seismic wave. In this study we measured the seismic anisotropy of different rocks, collected in the Alps. Our results show distinct differences between rocks of oceanic origin and those of continental origin.
Sina Hale, Xavier Ries, David Jaeggi, and Philipp Blum
Solid Earth, 12, 1581–1600, https://doi.org/10.5194/se-12-1581-2021, https://doi.org/10.5194/se-12-1581-2021, 2021
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The construction of tunnels leads to substantial alterations of the surrounding rock, which can be critical concerning safety aspects. We use different mobile methods to assess the hydromechanical properties of an excavation damaged zone (EDZ) in a claystone. We show that long-term exposure and dehydration preserve a notable fracture permeability and significantly increase strength and stiffness. The methods are suitable for on-site monitoring without any further disturbance of the rock.
Jessica A. McBeck, Wenlu Zhu, and François Renard
Solid Earth, 12, 375–387, https://doi.org/10.5194/se-12-375-2021, https://doi.org/10.5194/se-12-375-2021, 2021
Short summary
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The competing modes of fault network development, including nucleation, propagation, and coalescence, influence the localization and connectivity of fracture networks and are thus critical influences on permeability. We distinguish between these modes of fracture development using in situ X-ray tomography triaxial compression experiments on crystalline rocks. The results underscore the importance of confining stress (burial depth) and fluids on fault network development.
Hanaya Okuda, Ikuo Katayama, Hiroshi Sakuma, and Kenji Kawai
Solid Earth, 12, 171–186, https://doi.org/10.5194/se-12-171-2021, https://doi.org/10.5194/se-12-171-2021, 2021
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Serpentinite, generated by the hydration of ultramafic rocks, is thought to be related to slow earthquakes at the subduction plate interface in the mantle wedge. We conducted friction experiments on brucite, one of the components of serpentinite, and found that wet brucite exhibits low and unstable friction under low effective normal stress conditions. This result suggests that wet brucite may be key for slow earthquakes at the subduction plate interface in a hydrated mantle wedge.
Chaojie Cheng, Sina Hale, Harald Milsch, and Philipp Blum
Solid Earth, 11, 2411–2423, https://doi.org/10.5194/se-11-2411-2020, https://doi.org/10.5194/se-11-2411-2020, 2020
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Fluids (like water or gases) within the Earth's crust often flow and interact with rock through fractures. The efficiency with which these fluids may flow through this void space is controlled by the width of the fracture(s). In this study, three different physical methods to measure fracture width were applied and compared and their predictive accuracy was evaluated. As a result, the mobile methods tested may well be applied in the field if a number of limitations and requirements are observed.
Martijn P. A. van den Ende, Marco M. Scuderi, Frédéric Cappa, and Jean-Paul Ampuero
Solid Earth, 11, 2245–2256, https://doi.org/10.5194/se-11-2245-2020, https://doi.org/10.5194/se-11-2245-2020, 2020
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The injection of fluids (like wastewater or CO2) into the subsurface could cause earthquakes when existing geological faults inside the reservoir are (re-)activated. To assess the hazard associated with this, previous studies have conducted experiments in which fluids have been injected into centimetre- and decimetre-scale faults. In this work, we analyse and model these experiments. To this end, we propose a new approach through which we extract the model parameters that govern slip on faults.
Berend A. Verberne, Martijn P. A. van den Ende, Jianye Chen, André R. Niemeijer, and Christopher J. Spiers
Solid Earth, 11, 2075–2095, https://doi.org/10.5194/se-11-2075-2020, https://doi.org/10.5194/se-11-2075-2020, 2020
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The strength of fault rock plays a central role in determining the distribution of crustal seismicity. We review laboratory work on the physics of fault friction at low shearing velocities carried out at Utrecht University in the past 2 decades. Key mechanical data and post-mortem microstructures can be explained using a generalized, physically based model for the shear of gouge-filled faults. When implemented into numerical fault-slip codes, this offers new ways to simulate the seismic cycle.
Caiyuan Fan, Jinfeng Liu, Luuk B. Hunfeld, and Christopher J. Spiers
Solid Earth, 11, 1399–1422, https://doi.org/10.5194/se-11-1399-2020, https://doi.org/10.5194/se-11-1399-2020, 2020
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Coal is an important source rock for natural gas recovery, and its frictional properties play a role in induced seismicity. We performed experiments to investigate the frictional properties of bituminous coal, and our results show that the frictional strength of coal became significantly weakened with slip displacement, from a peak value of 0.5 to a steady-state value of 0.3. This may be caused by the development of shear bands with internal shear-enhanced molecular structure.
Maximilian O. Kottwitz, Anton A. Popov, Tobias S. Baumann, and Boris J. P. Kaus
Solid Earth, 11, 947–957, https://doi.org/10.5194/se-11-947-2020, https://doi.org/10.5194/se-11-947-2020, 2020
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In this study, we conducted 3-D numerical simulations of fluid flow in synthetically generated fractures that statistically reflect geometries of naturally occurring fractures. We introduced a non-dimensional characterization scheme to relate fracture permeabilities estimated from the numerical simulations to their geometries in a unique manner. By that, we refined the scaling law for fracture permeability, which can be easily integrated into discrete-fracture-network (DFN) modeling approaches.
Bjarne S. G. Almqvist, Hagen Bender, Amanda Bergman, and Uwe Ring
Solid Earth, 11, 807–828, https://doi.org/10.5194/se-11-807-2020, https://doi.org/10.5194/se-11-807-2020, 2020
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Rocks in fault zones can melt during earthquakes. The geometry and magnetic properties of such earthquake-melted rocks from Jämtland, central Sweden, show that they formed during Caledonian mountain building in the Palaeozoic. The small sample size (~0.2 cm3) used in this study is unconventional in studies of magnetic anisotropy and introduces challenges for interpretations. Nevertheless, the magnetic properties help shed light on the earthquake event and subsequent alteration of the rock.
David Healy, Nicholas Erik Timms, and Mark Alan Pearce
Solid Earth, 11, 259–286, https://doi.org/10.5194/se-11-259-2020, https://doi.org/10.5194/se-11-259-2020, 2020
Short summary
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Rock-forming minerals behave elastically, a property that controls their ability to support stress and strain, controls the transmission of seismic waves, and influences subsequent permanent deformation. Minerals are intrinsically anisotropic in their elastic properties; that is, they have directional variations that are related to the crystal lattice. We explore this directionality and present new ways of visualising it. We hope this will enable further advances in understanding deformation.
Mathieu Soret, Philippe Agard, Benoît Ildefonse, Benoît Dubacq, Cécile Prigent, and Claudio Rosenberg
Solid Earth, 10, 1733–1755, https://doi.org/10.5194/se-10-1733-2019, https://doi.org/10.5194/se-10-1733-2019, 2019
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This study sheds light on the mineral-scale mechanisms controlling the progressive deformation of sheared amphibolites from the Oman metamorphic sole during subduction initiation and unravels how strain is localized and accommodated in hydrated mafic rocks at high temperature conditions. Our results indicate how metamorphic reactions and pore-fluid pressures driven by changes in pressure–temperature conditions and/or water activity control the rheology of mafic rocks.
Camille Parlangeau, Alexandre Dimanov, Olivier Lacombe, Simon Hallais, and Jean-Marc Daniel
Solid Earth, 10, 307–316, https://doi.org/10.5194/se-10-307-2019, https://doi.org/10.5194/se-10-307-2019, 2019
Short summary
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Calcite twinning is a common deformation mechanism that mainly occurs at low temperatures. Twinning activation appears at a critical strength value, which is poorly documented and still debated. Temperature is known to influence twin thickness and shape; however, few studies have been conducted on calcite deformation at low temperatures. The goal of this work is to determine if thickness is mainly due to high temperatures and to establish the validity of a threshold twinning activation value.
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Short summary
Triaxial compression tests at different effective stresses allow for analysing the deformation behaviour of Opalinus Clay, the potential host rock for nuclear waste in Switzerland. We conducted microstructural investigations of the deformed samples to relate the bulk hydro-mechanical behaviour to the processes on the microscale. Results show a transition from brittle- to more ductile-dominated deformation. We propose a non-linear failure envelop associated with the failure mode transition.
Triaxial compression tests at different effective stresses allow for analysing the deformation...
