Why should this figure represent a thrust fault?

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I know this might be a stupid question, but I really want to understand. Since thrust faults are reverse faults why in the figure above if we turned the photo 90 degrees clockwise like this

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we don't get the same shape as this

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I think that in faults in general the fault plane is inclined to the horizontal, and the hanging wall is the mass of rocks above the fault plane, i.e., the side at which the angle between the fault plane and the horizontal is larger, and the foot wall is the mass of rocks below the fault plane, i.e., the side at which the angle between the fault plane and the horizontal is smaller. In the second figure, we have a hanging wall on the left side and we have a foot wall on the right side, and it seems that the hanging wall is moving down relative to the foot wall, and that's what happens in normal faults not reverse ones, right? So why we consider the thrust fault in figure one as a reverse fault?

  • $\begingroup$ you do get the same shape, look at the bedding if you drilled through it, the bedding would be doubled, that is a thrust fault. It is a result of compression forces. You can't rotate the blocks without also rotating your orientation to the bedding planes. $\endgroup$
    – John
    Commented Jun 13, 2017 at 21:44

1 Answer 1


First don't rotate the whole thing, you are just confusing yourself by rotating the bedding plane. You can't rotate the bedding planes and expect faults to match up like that. Your eye is treating the bedding plane as horizontal which makes it a completely different from of fault.

A thrust fault is just a reverse fault with a shallow fault angle. enter image description here

Pay attention to how the bedding planes move relative to each other notice how they begin to double up in both forms of reverse fault, while in a normal fault sections begin to disappear in the middle, being lost from hypothetical drill core entirely. In the reverse faults if you drilled down through the blocks there are areas where you would drill through the dark central bed twice while in the normal there are places where you would never hit it at all.


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