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Journal Article

Stress state at faults: the influence of rock stiffnesscontrast, stress orientation, and ratio

Authors
/persons/resource/mziegler

Ziegler,  M.
2.6 Seismic Hazard and Risk Dynamics, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Seithel,  Robin
External Organizations;

Niederhuber,  Thomas
External Organizations;

/persons/resource/heidbach

Heidbach,  O.
2.6 Seismic Hazard and Risk Dynamics, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Kohl,  Thomas
External Organizations;

Müller,  Birgit
External Organizations;

Rajabi,  Mojtaba
External Organizations;

Reiter,  Karsten
External Organizations;

Röckel,  Luisa
External Organizations;

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5028650.pdf
(Publisher version), 8MB

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Citation

Ziegler, M., Seithel, R., Niederhuber, T., Heidbach, O., Kohl, T., Müller, B., Rajabi, M., Reiter, K., Röckel, L. (2024): Stress state at faults: the influence of rock stiffnesscontrast, stress orientation, and ratio. - Solid Earth, 15, 8, 1047-1063.
https://doi.org/10.5194/se-15-1047-2024


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5028650
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 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.