Okay so I don't know why link didn't show up when I put in the URL box so just paste it into your browser I guess..

http://quake.usgs.gov/prepare/future/respond/index.html

and the quote from the site:

"On June 27, 1988, and August 8, 1989, there were two earthquakes of magnitude 5.0 and 5.2 near the Santa Cruz Mountains segment of the San Andreas fault. In both cases, scientists were concerned that these events could be foreshocks to a larger earthquake because of their magnitude and their position. Foreshocks do occur less than 5 days before about half of the large earthquakes in California. For these reasons, the California Office of Emergency Services issued an advisory of an increased likelihood of a major earthquake within the next 5 days following those quakes. The Loma Prieta earthquake of October 17, 1989, was a little late, but it was the quake anticipated by the advisories. "