Exercise 6
Based on the limestone Mohr diagram below that was taken from the solution of Exercise 3, answer the following questions.
a) What type of fractures will be formed under the stress conditions represented by the Mohr circle number 1? What will be the tectonic regime and the orientation of the fractures for the following three situations:
- when σ1 is vertical and σ3 is horizontal and strikes EW;
- when σ1 and σ3 are horizontal and strike NS and EW, respectively; and,
- when σ3 is vertical and σ1 strikes EW?
Enter your answers in the table below and make drawings representing the stresses and the resulting fractures in each case.
|
Stress orientation |
Tectonic regime |
Fracture strike |
Fracture dip |
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σ1 is vertical σ3 is horizontal and strikes EW |
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σ1 is horizontal and strikes NS σ3 is horizontal and strikes EW |
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σ3 is vertical σ1 is horizontal and strikes EW |
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b) What type of fractures will be formed under the stress conditions represented by Mohr circle number 2? What will be the tectonic regime and the orientation of the fractures for the following three situations:
-
-
-
when σ1 is vertical and σ3 is horizontal and strikes EW;
-
when σ1 and σ3 are horizontal and strike NS and EW, respectively; and,
-
when σ3 is vertical and σ1 strikes EW?
-
-
Answer this question using the table below and make drawings representing the stresses and the resulting fractures in each case.
|
Stress orientation |
Tectonic regime |
Fracture strike |
Fracture dip |
|
σ1 is vertical σ3 is horizontal and |
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σ1 is horizontal and σ3 is horizontal and |
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σ3 is vertical σ1 is horizontal and |
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