Faults are surfaces in the Earth al

Faults are surfaces in the Earth along which one side
moves or has moved with respect to the other. They are
identified either when an earthquake occurs or by geological
mapping showing that motion across the fault
has occurred in the past. Many faults are inactive, in the
sense that there has been no motion across them within
some defined time interval, typically the past million
years or less. Other faults are active, in the sense that
recent motion has occurred and hence motion might be
expected in the future. Faults, and the earthquakes
on them, are studied to understand both the regional
tectonics and the mechanics of faulting