Final answer:
Depressions in fracture zones are useful in mapping the direction of plate motion because they tend to be faults or fault zones.
Step-by-step explanation:
Depressions in fracture zones are useful in mapping the direction of plate motion because they tend to be faults or fault zones. Faults are fractures through rocks that have had a significant amount of movement on them, while fault zones are areas with multiple brittle fractures. By studying these fracture zones, scientists can determine the direction and magnitude of plate motion.