Looks like Scientific American is now giving away old articles. Why not, their marginal cost is zero! This one is a 2004 article on silent earthquakes.
I always find SciAm articles to be too wordy, and I can't stand reading them, but there is neat stuff here, if you want to wade through it. I don't think that silent earthquakes now have the glamour they had 4 years ago, but they are an interesting part of the earthquake ecology.
Since we've always had these around, it's tough to tell if they mean anything. There's been an annual event under Vancouver, ever since they could measure them. To me, the interesting part is the installation of real-time GPS, required to record them.