gps - Is there a geodetic benchmark that is fixed with respect to plate tectonics?

I see that NGS benchmarks are used to monitor the movement of geologic plates.

Is one of the benchmarks assumed to be in a fixed location, with movements of all other benchmarks measured with respect to it, or are all benchmarks moving as a result of plate tectonics?

Answer

The IERS reference meridian is a weighted average of ground-based monitoring stations. Thus, tectonic monitoring must involve the motion of one's own plate relative to this global average motion.