Such variable fault behavior is being widely recognized in continental interiors. In many places large earthquakes cluster on specific faults for some time and then migrate to others.
The gist of this opinion is that age-old problem of apparent strain for New Madrid and other interior earthquake zones. At the heart of the problem is the question of how long these zones have been active at the rates now observed. New GPS studies have shown virtually no regional strain rate for the New Madrid area.
They are essentially proposing that all these zones flick on and off like Christmas lights. The implications are that the existing zones have shot their load and are now 'dead'. All of the measured seismicity is aftershock activity. The next big earthquakes will appear suddenly in some other magical zone, of which we have nary a clue!
This opinion is now entrenched the same as Global Cottage Warming (Ha!). Although I have written extensively of my model for ENA seismicity, the fight has gone out of me. People within these zones can now be like Toronto, and do nothing.