Moritz O. Ziegler, Robin Seithel, Thomas Niederhuber, Oliver Heidbach, Thomas Kohl, Birgit Müller, Mojtaba Rajabi, Karsten Reiter, Luisa Röckel
{"title":"Stress state at faults: the influence of rock stiffness contrast, stress orientation, and ratio","authors":"Moritz O. Ziegler, Robin Seithel, Thomas Niederhuber, Oliver Heidbach, Thomas Kohl, Birgit Müller, Mojtaba Rajabi, Karsten Reiter, Luisa Röckel","doi":"10.5194/se-15-1047-2024","DOIUrl":null,"url":null,"abstract":"Abstract. The contemporary crustal stress state is primarily driven by gravitational volume forces and plate tectonics. However, there are various smaller-scale sources such as geological structures and stiffness contrast that perturb stresses and deviate them from the regional pattern. For example, borehole stress analysis in numerous cases has revealed abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. Herein, we investigate the rotation of principal stress axes at a fault by means of a 2D generic numerical model. We focus on the near field of the fault and the damage zone with a fault parameterized as a rock stiffness contrast. A substantial influence of the far-field stress field in terms of the differential stress and in terms of the stress ratio RS=S1/S_3 is shown. Furthermore, the contrast in material properties is the basis for any stress rotation, and in particular the stiffness is demonstrated to have a significant influence. Eventually, the impact of the angle between the fault strike and the orientation of SHmax is demonstrated. Our results show that the stress rotation is negatively correlated with the ratio of principal far-field stresses. A small angle between the far-field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general the findings are in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow-dipping faults.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Solid Earth","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5194/se-15-1047-2024","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract. The contemporary crustal stress state is primarily driven by gravitational volume forces and plate tectonics. However, there are various smaller-scale sources such as geological structures and stiffness contrast that perturb stresses and deviate them from the regional pattern. For example, borehole stress analysis in numerous cases has revealed abrupt rotations of horizontal stress orientation of up to 90° when faults are crossed. Herein, we investigate the rotation of principal stress axes at a fault by means of a 2D generic numerical model. We focus on the near field of the fault and the damage zone with a fault parameterized as a rock stiffness contrast. A substantial influence of the far-field stress field in terms of the differential stress and in terms of the stress ratio RS=S1/S_3 is shown. Furthermore, the contrast in material properties is the basis for any stress rotation, and in particular the stiffness is demonstrated to have a significant influence. Eventually, the impact of the angle between the fault strike and the orientation of SHmax is demonstrated. Our results show that the stress rotation is negatively correlated with the ratio of principal far-field stresses. A small angle between the far-field stress orientation and the fault facilitates stress rotation. A high contrast in rock stiffness further increases the stress rotation angle. Faults striking perpendicular to the maximum principal stress orientation experience no rotation at all. However, faults oriented parallel to the maximum principal stress orientation experience either no rotation or a 90° rotation, dependent on the ratio of principal stresses and the rock stiffness contrast. A comparison with observations from various boreholes worldwide shows that in general the findings are in agreement, even though the dip angle proves to have an influence on the stress rotation, in particular for shallow-dipping faults.
期刊介绍:
Solid Earth (SE) is a not-for-profit journal that publishes multidisciplinary research on the composition, structure, dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. The journal invites contributions encompassing observational, experimental, and theoretical investigations in the form of short communications, research articles, method articles, review articles, and discussion and commentaries on all aspects of the solid Earth (for details see manuscript types). Being interdisciplinary in scope, SE covers the following disciplines:
geochemistry, mineralogy, petrology, volcanology;
geodesy and gravity;
geodynamics: numerical and analogue modeling of geoprocesses;
geoelectrics and electromagnetics;
geomagnetism;
geomorphology, morphotectonics, and paleoseismology;
rock physics;
seismics and seismology;
critical zone science (Earth''s permeable near-surface layer);
stratigraphy, sedimentology, and palaeontology;
rock deformation, structural geology, and tectonics.