Certainly "proving it works" is the primary focus.

Ringmap is just a way to assist in the evaluation process.

Your suggestion is a good one but the process would be cumbersome at best. Whoever wanted to do it would need my database or a cumulative file like NEIC uses. That's a big gulp to begin with.

Then the file would be circle-searched twice for each ring, subtracting out the common quakes to leave the "ring" quakes. Finally the probability would be calculated for the ring quakes.

Then repeat for the next ring.

No small task but a worthwhile one IMHO. I'm not comfortable with a probability based on area alone. All areas are not seismically equal, after all....

Roger