- © 2007 by the Seismological Society of America
There have been a wide variety of approaches applied to forecasting earthquakes (Turcotte 1991; Kanamori 2003). These approaches can be divided into two general classes. The first is based on empirical observations of precursory changes. Examples include precursory seismic activity, precursory ground motions, and many others. The second approach is based on statistical patterns of seismicity. Neither approach has been able to provide reliable short-term forecasts (days to months) on a consistent basis.
Although short-term predictions are not available, longer-term seismic-hazard assessments can be made. A large fraction of all earthquakes occur in the vicinity of plate boundaries, although some do occur in plate interiors. It is also possible to assess the long-term probability of having an earthquake of a specified magnitude in a specified region. These assessments are primarily based on the hypothesis that future earthquakes will occur in regions where past, typically large, earthquakes have occurred (Kossobokov et al. 2000). As we will discuss, a more promising approach is to begin with the hypothesis that the rate of occurrence of small earthquakes in a region can be analyzed to assess the probability of occurrence of much larger earthquakes.
The Regional Earthquake Likelihood Models (RELM) forecast described in this paper is primarily based on the pattern informatics (PI) method (Rundle et al. 2002, 2003; Tiampo et al. 2002a, 2000c). This method identifies regions of strongly correlated fluctuations in seismic activity. These regions are the locations where subsequent large earthquakes have been shown to occur, therefore indicating a strong association with the high stress preceding the main shock. The fluctuations in seismicity rate revealed in a PI map may be related to the preparation process for large earthquakes. Seismic quiescence and seismic activation (Bowman et al. 1998; Wyss and Habermann 1988), which are revealed by …