We need to fix a reference frame, for measuring things.
In earthquake science, both the earthquake rupture and the magnitude are indirect measures, their standards evolve with the technology.
Some years ago we have started by reasoning about the existing rupture vs magnitude relationships , and how we can improve them, with new data derived from uniform processing.
We don’t have much more than that right now.
But if you are interested in this topic, if you published, or are interested to publish studies on it, please contact the reference person of this technical lab.
FAULT2SHA WG is happy to have you onboard!
 Taken from the materials of the 3rd Fault2SHA Workshop held in Barcelonnette (F), May 2-4, 2017, available here https://fault2shablog.wordpress.com/2017/06/23/workshop-materials-online/