The 1983 Coalinga earthquake indeed may have released enough strain to delay the Parkfield earthquake. Or one might argue that the shaking and stress redistribution of the Coalinga quake raised the probabilities of earthquakes on all the surrounding faults for a while.

But it can be surprising how many theories show up only after an expected event has failed to appear. I wouldn't be surprised if one could equally well argue that the Coalinga event, in concert with viscous relaxation in the lower crust, might have advanced rather than delayed the clock. After all, the 1992 Landers event unloaded much of the Hector Mine fault plane, but it nevertheless broke 7 years later.

John