John,, I've heard about M8 for a long time, but don't know enough about it. It is taken seriously enough that someone was funded by (Knopoff???) SCEC to evaluate it-quite a long time ago-5 years or more. The seismicity patterns you mention sound plausible-like they could mean something. Lowell Whiteside probably knows a lot about M8-I probablyh first heard about it from him 15 years ago.