The ratio of strike slip to dip slip is a function of the net slip on a fault. Assuming that the Basin and Range province of southwestern Arizona lies within a zone of deformation between the North American and Pacific plates, this ratio suggests the existence of strike-slip components of movement on range-bounding faults in this area. Across southwestern Arizona, estimates yield ∼20 km of strike-slip offset since late Eocene time (30 m.y. B.P.).