These faults can act like railroad tracks controlling the future direction the tectonic plate moves in. It may also mean plates can rotate one way more easily than another, as there is less tectonic resistance for the plate to turn in one direction - away from the fault - than the other.
A magnitude 6 earthquake struck eastern Afghanistan near the border with Pakistan just before midnight local time on Sunday, according to the United States Geological Survey. Several aftershocks followed. At least 800 people were killed and 2,500 were injured. The epicentre of the earthquake was at a depth of about 8km (5 miles), which seismologists consider shallow, making the ground shaking more intense and destructive, particularly for fragile homes and communities.