Articles | Volume 11, issue 3
https://doi.org/10.5194/se-11-807-2020
© Author(s) 2020. 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-11-807-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
07 May 2020
Research article |
| 07 May 2020
| 07 May 2020
Magnetic properties of pseudotachylytes from western Jämtland, central Swedish Caledonides
Bjarne S. G. Almqvist
CORRESPONDING AUTHOR
Department of Earth Sciences, Geophysics, Villavägen 16, 752 36
Uppsala, Sweden
Hagen Bender
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
Amanda Bergman
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
Ramböll Sverige AB, Box 17009, Krukmakargatan 21, 104 62
Stockholm, Sweden
Uwe Ring
Department of Geological Sciences, Stockholm University, 106 91
Stockholm, Sweden
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Martijn P. A. van den Ende, Marco M. Scuderi, Frédéric Cappa, and Jean-Paul Ampuero
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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
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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
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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.
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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.
David Healy, Nicholas Erik Timms, and Mark Alan Pearce
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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
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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
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.
Rocks in fault zones can melt during earthquakes. The geometry and magnetic properties of such...
