Answer:
the crust of the lithosphere that has fractured along plate boundaries and ridges
Step-by-step explanation:
Fault lines, also known as geological faults, are fractures in the rock blocks that make up the earth's surface, causing them to suffer relative displacements in their structures. These fractures are almost always formed by the action of internal relief agents and can manifest both in areas under strong tectonism and in more stable regions. In other words, we can say that the fault lines are the crust of the lithosphere that fractured along the plate boundaries and grooves.