Every once in a while I look at my wikipedia articles, and see if all the life has been stripped out of them. I started many articles there at one time, and always got in trouble with the humorless editors! Writing an article is like throwing it over the wall, and letting others hack away at it. Nearly all my articles have grown beyond recognition, but this one remains virtually untouched. Must be my pretty pictures!
The main point is that water makes these zones grow, and thus they are unlocked, and can grow forever. The alternative hypothesis is that all these historic zones are locked, and can never produce another earthquake. Thus, we must look to totally virgin rock for the next big quake. ---- Ha, ha!