Cathryn,
you asked for comment....I'm sort of repeating my earlier comment. I think a repository for observations as you now discuss is a much better idea than a repository for predictions. But, I think you and Petra have the following problem: If it is not "blind", then it will not be as scientific. For example, if someone notices that oil is seeping out of the San Cayetano fault at Silverthread Oil field between Ojai and Santa Paula, then suddenly everyone will start posting on what their cat is doing. And, at least 15 years ago, oil is always seeping there (and elsewhere). I think it is only after a large earthquake that people (possibly scientists) will go back and loook at this repository. The problem is, if it is blind, then people won't post, because there will be no response/no interaction. So, my guess is you will have it so everyone can see the posts.
I still think you should try first for people to post on this board....if you get too many of these kind of posts that other subjects are drowned out, then you can see that there is enough interest to start a new web page. I have my doubts that you will get a large number of people supplying observations...you would probably want 100s in just California.
Chris