Though I agree the foreshocks were precursory (it could hardly have been coincidence), it has never been my position that precursory events do not occur before some large quakes. Besides, you specifically stated "[there] might have seen some sort of signal in addition to the foreshocks."

With a re-reading of your post, I can see your reasoning - "since there were foreshocks, there might have been some other precursory phenomena." I just don't agree with it - at least that the existence of foreshocks make it more likely that some other phenomenon was present.

My position has always been that studying precursory events will never lead to reliable earthquake forecasting, since "even the quake doesn't know it's going to happen until it does." There may be occasional successes when stress has reached extraordinarily large levels; certain phenomenon may then occur that, all taken together, make the probability of a large quake rather high.

In the case you mentioned, I believe it likely there was simply a domino-effect, with stress being transferred from one asperity to another, as each broke. There would have been no way to know in advance whether the increased stress on each asperity would be sufficient to cause it to break.

Mike Williams