the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Understanding the stress field at the lateral termination of a thrust fold using generic geomechanical models and clustering methods
Abstract. This study employs numerical simulations based on the Limit Analysis (LA) method to calculate the stress distribution in a kilometric-scale model developed over a basal detachment, featuring the lateral termination of a generic fault under compression. We conduct 2500 2D and 500 3D simulations, varying basement and fault friction angles, to analyze and classify the results into clusters representing similar failure patterns to understand the stress fields. Automatic fault detection methods are employed to identify the number and positions of fault lines in 2D and fault surfaces in 3D. Clustering approaches are utilized to group the models based on the detected failure patterns. For the 2D models, the analysis reveals three primary clusters and five transitional ones, qualitatively consistent with the critical Coulomb wedge theory and the influence of inherited structural and geometric aspects over rupture localization. In the 3D models, four different clusters portray the lateral prolongation of the inherited fault. High stress magnitudes are detected between the compressive boundary and the activated or created faults, and at the root of the inherited active fault. Tension zones appear near the outcropping surface relief while stress decreases with depth at the footwall of the created back-thrusts. A statistical, cluster-based stress field analysis indicates that for a given cluster, the stress field mainly conserves the same orientations, while the magnitude varies with changes in friction angles and compressive field intensity, except in failure zones where variations are sparse. Small parametric variations could lead to significantly different stress fields, while larger deviations might result in similar configurations. The comparison between 2D and 3D models shows the importance of lateral stresses and their influence on rupture patterns, distinguishing between 3D analysis and 2D cross-sections. Lastly, despite using small-scale models, stress field variations over a span of a couple of kilometers are quite large.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2024-1906', Anonymous Referee #1, 23 Jul 2024
Dear Editor, dear authors,
please find some comments to the manuscript egusphere-2024-1906 in the supplement.
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AC1: 'Reply on RC1', Anthony Adwan, 30 Jul 2024
Dear referee,
First of all, we would like to thank you for your constructive review. We are carefully revising our manuscript based on your comments and we will be posting our reply as soon as possible.
Nonetheless, I would like to apologize for the delay, but the majority of my co-authors are on vacation and thus I must wait for their intake before submitting our answer.
Thank you for understanding,
Citation: https://doi.org/10.5194/egusphere-2024-1906-AC1 - AC3: 'Reply on RC1', Anthony Adwan, 22 Sep 2024
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AC1: 'Reply on RC1', Anthony Adwan, 30 Jul 2024
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RC2: 'Comment on egusphere-2024-1906', Anonymous Referee #2, 08 Aug 2024
Thank you to the authors for their interesting study. However, I have some concerns regarding the assumptions and methodology. Without clarification, it is difficult for me to discuss the results. I have outlined my concerns as follows:
- Please clearly state the application of the current study. How does it help to characterize the specific site?
- In all cases, the dip angles are constant. What would happen if these parameters were to change?
- Line 48: What do you mean by “homogeneous categories”? What is homogeneous within these categories?
- Line 53: How did you define the deviatoric stress?
- What is the initial state of stress in the system? When there is a fault and wedge-shaped structures, the system has already experienced stress changes. See the following paper:
- The evolution of pore pressure, stress, and physical properties during sediment accretion at subduction zones.
- Line 64: Did you evaluate the capability of the “uniform bulk Coulomb material” in modeling real cases or sandbox models within the proposed framework of this manuscript? Please include the validation results.
- Line 72: How does “Optum CE” work? Which equations are considered? How does it discretize the equations? Is there any mesh refinement scheme used? Please provide a summarized explanation.
- Line 75: I noticed that the applied load is unknown, so I assume that a fixed displacement rate was implemented. Please mention this. Also, how did you verify the stability and mesh independence of the results? I noticed that a similar mesh was used for all cases.
- For 2D, 10,000 elements were used, while for 3D, 40,000 elements were considered. Are the element sizes the same in both cases? If not, on what basis are the results compared? Furthermore, the mesh dependency analysis for the 3D cases is unclear, and the stability analysis is not included. Without this information, the accuracy of the results and the impact of boundary conditions are questionable (at least for me).
- Line 148: In all cases, back-thrust is observed. However, in the literature, there are instances where back-thrusting does not occur. If the entire range of parameters is explored, some cases would likely show no back-thrust. Clarification is needed here. See the following paper:
- Control of décollement strength and dip on fault vergence in fold-thrust belts and accretionary prisms.
- Pore pressure and overpressure development are not considered. What would happen if these parameters were included? What is the sensitivity of the conclusions to this parameter?
Citation: https://doi.org/10.5194/egusphere-2024-1906-RC2 - AC2: 'Reply on RC2', Anthony Adwan, 22 Sep 2024
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