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Joints (GREEN).
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The tip of a growing joint is always perpendicular to
3 at the joint tip
during propagation.
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Curved joints indicate temporal and/or spatial
variations in the orientation of
3 during joint growth.
Faults (RED).
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New faults in virgin rock form in each lithology
with an approximately constant acute angle between
1 and the two conjugate
fault orientations. This angle ranges from 25° to 40° but is normally about 30°.
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Pre-existing discontinuities with a wide range of
orientations can be activated as faults, provided they are not oriented perpendicular to a principal stress.
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Deformation bands (faults with an anti-mode I
component) also tend to form at 30° to
1 but can form at
any angle <90°.
Stylolites (BLUE) and
compaction bands (not shown) form perpendicular to
1.
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