Over the last 1,000 years, the fault has had major earthquakes about every 140 years. The last major earthquake on the Hayward fault was the great earthquake of 1868, which was (as of 2013) 145 years ago, suggesting to many that it's "due" for another one.
The Hayward fault is a strike-slip fault, meaning most of the movement is horizontal. There is about 8-10mm of aseismic creep (movement not during an earthquake) along the fault per year. Not enough for dramatic effects, but enough to crack sidewalks and twist doorways.
Links and References
- Hayward Fault Fact Sheet (California Geological Survey)
- Hayward Fault (Wikipedia)
- Active Traces of the Hayward Fault USGS. Includes maps and Google Earth virtual tour
- Hayward Fault in Oakland on about.com
- The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) (USGS)