Hi John - somewhere in this site there is the answer to your question. The Ringmap is a graphical representation of Far Field Aftershock rings as given by Lowell Whiteside. Roger was gracious and wrote a program to display them on a map. You can download his program from a link at his web site: http://www.freewebs.com/rogerhweb/

If you search the site using the function at the top of the page for FFA you might find the distances listed. I'm pretty sure that was all posted here.

Roger may have the info readily available.

Canie