Question

If a dextral strike-slip fault system has a right step-over, which one of the following features will develop?

• A. Zone of reverse fault
• B. Releasing bend
• C. Restraining bend
• D. Contractional duplex

Hint:

Recall the Salton Trough example: a right step in a dextral fault pulls the ground apart rather than squeezing it.

Answer 1

The Correct Option is B

This question tests the rule that links slip sense and step direction in strike-slip faults to the type of bend that forms. A fault system rarely runs in one straight line, its segments step left or right, and that step can either open the ground up or squeeze it together.

1. Zone of reverse fault: reverse faults belong to a compressional setting, which is the restraining case, not what a right step on a dextral fault gives.
2. Releasing bend: for a right-lateral fault, a right step drags the two fault strands apart, opening a gap that stretches and drops down. This is the releasing bend, often filled by a pull-apart basin such as the Salton Trough on the San Andreas system.
3. Restraining bend: this compressional bend forms at a left step on a dextral fault, since the segments are pushed into each other there instead of being pulled apart.
4. Contractional duplex: this is a stack of thrust slices built in a restraining, compressional setting, again the opposite of what a right step on a dextral fault produces.

Working through the geometry, a right-lateral fault stepping right always creates space, not squeeze, between the overlapping strands.

Let's summarize:

• Dextral fault, right step: releasing bend, extension, pull-apart basin.
• Dextral fault, left step: restraining bend, compression, uplift or duplex.

So a right step-over in a dextral strike-slip system develops a releasing bend.