Where is most of the stretching, or strain, happening in the western US?

There is only a very small amount of stretching currently happening in the Basin and Range Province. Scientists think that most of the stretching happened from 30 to 5 million years ago, and that most of the current strain is occurring at the western and eastern edges of the Basin and Range Province. The greatest motion is on the western edge and appears to be shearing (side to side motion) more than stretching.