Answer: non-shifting lines indicate non moving star.
Explanation: when a star is moving toward the detector, the wavelength will decrease - there will be a blue shift.
When it's moving away from the earth or detector, the wavelength will increase - there will be a red shift.
Identifiable patterns of absorption lines that appear shorter or longer wavelengths than normal indicate that the star is moving
In visualisation, the bottom spectrum shows the normal position of absorption line for a star that is not moving toward or away from the earth.