These faults usually occur in areas where a plate is very slowly splitting apart or where two plates are pulling away from each other. Strike-slip faults are the cracks between two plates that are sliding past each other. You can find these kinds of faults in California. The San Andreas fault is a strike-slip fault. It's the most famous California fault and has caused a lot of powerful earthquakes.
Reverse faults are cracks formed where one plate is pushing into another plate.
They also occur where a plate is folding up because it's being compressed by another plate pushing against it. At these faults, one block of rock is sliding underneath another block or one block is being pushed up over the other.