All lines on the plane are plunging, except the strike line. Lines 2 and 4 are referred to as the apparent dip , and are always less than the true dip. It is expressed in degrees and direction. Note that the dip line and the strike line are 90 degrees from one another. When stress builds up in a rock, it will break.
Faults are the product of compressional, tensional or shear stress.
There are several types of faults that occur, depending on where and how the stress is placed on the rock. Normal faults are caused by tensional forces and reverse faults are caused by compressional forces. Direction of movement is parallel to the strike. If an observer stands on one side of the fault and sees a person move with the fault on the other side, depending on the direction that person appears to move, will be the classification of the fault . Dip-slip normal fault.