What does the dip angle represent?

The dip angle is a crucial concept in geology and civil engineering, particularly when analyzing faults and subsurface formations. It represents the angle at which a geological layer or fault plane is inclined relative to the horizontal plane. Essentially, it indicates how steeply a fault or layer dips beneath the earth's surface.

While the other options present important geological concepts, they do not accurately describe the characteristic of dip angle. The dip angle does not pertain to the depth of the focus of an earthquake, the angle of the fault line itself, or the distance of ground displacement caused by tectonic movements. Instead, it specifically refers to how geological layers or faults are oriented in terms of their angle of descent from the horizontal.