It must be remembered that there is currently no way to predict earthquakes! Earthquake monitoring and prediction is still in its infancy.
So if you are after advance warning, then forget it. No-one knows when and where the next earthquake will happen.
However, “The Big One” has been predicted for some while now, so it is advisable to take suitable precautions. Reading this good article called Earthquake Safety and Preparedness in Los Angeles will help you be ready when it comes.
Also download the Earthquake Preparedness Handbook from LAFD.
L.A. Times article has an article on newest guidelines for earthquake preparedness.
Quakes Global Incident map. The latest quakes from around the world.
USGS live quakes Another version of above.
And finally, if you really want to scare yourself unnecessarily: Quake Prediction for Los Angeles.