> at least to predict that a quake we see is likely to be a precursor to a much larger one or is likely that peak.

That we can basically do. "Observations show that the chance of an earthquake being followed by a larger one nearby and within a week is about 5%."

https://www.usgs.gov/faqs/what-probability-earthquake-a-fore...

It is an incredibly safe bet that any earthquake is not the sign of a larger one.