Hi Canie. This has always been the problem I have had with the “time predictable” theory.

Using Parkfield as an example. What caused the last M>6.0 there in 1966 is no longer there. It was destroyed when the quake occurred. However long it takes the creep to reach the next point where that section of the fault can no longer move will be the next location of a large, or major quake.

It may be that the point of the next quake has already been reached, but it is much larger then the previous one’s so it’s going to take more energy to break the rock (s) and that’s why the next quake didn’t occur when they thought if would.

For the most part there appears to be a steady rate of creep in the area, with the exception of one area. This is in the area of Chalome. There could be other areas as creep is measured from the surface and not at the depth where the quakes occur.

It could also be that the Coalinga quake of 1983 released enough stress in the area that that brought the Parkfield area back from the threshold of a large quake. There could be any number of other reasons that could cause a change in the interval. Take Care…Don in creepy town