  We present a RELM forecast of future earthquakes in California that is
primarily based on the pattern informatics (PI) method. This method identifies
regions that have systematic fluctuations in seismicity, and it has been
demonstrated to be successful. A PI forecast map originally published on 19
February 2002 for southern California successfully forecast the locations of
sixteen of eighteen M>5 earthquakes during the past three years. The method has
also been successfully applied to Japan and on a worldwide basis. An
alternative approach to earthquake forecasting is the relative intensity (RI)
method. The RI forecast map is based on recent levels of seismic activity of
small earthquakes. Recent advances in the PI method show considerable
improvement, particularly when compared with the RI method using relative
operating characteristic (ROC) diagrams for binary forecasts. The RELM
application requires a probability for each location for a number of magnitude
bins over a five year period. We have therefore constructed a hybrid forecast
in which we combine the PI method with the RI method to compute a map of
probabilities for events occurring at any location, rather than just the most
probable locations. These probabilities are further converted, using
Gutenberg-Richter scaling laws, to anticipated rates of future earthquakes that
can be evaluated using the RELM test.
