LONG-TERM PROBABILISTIC FORECASTING OF EARTHQUAKES

We estimate long-term worldwide earthquake probabilities by extrapolat ing catalogs of seismic moment solutions. We base the forecast on corr elations of seismic moment tensor solutions. The forecast is expressed as a map showing predicted rate densities for earthquake occurrence a nd for focal mechanism orientation. Focal mechanisms are used first to smooth seismicity maps to obtain expected hazard maps and then to for ecast mechanisms for future earthquakes. Several types of smoothing ke rnels are used: in space domain we use the 1/distance kernel for the d istribution of seismicity around any epicenter. The kernel is paramete rized using two adjustable parameters: maximum distance and directivit y (distribution of seismicity around an epicenter with regard to the f ocal mechanism of an earthquake). For temporal prediction we use the P oisson hypothesis of earthquake temporal behavior. We test these forec asts: we use the first half of a catalog to smooth seismicity level, a nd the second half of the catalog is used to validate and optimize the prediction. To illustrate the technique we use available data in the Harvard catalog of seismic moment solutions to evaluate seismicity map s for several seismic regions. The method can be used with similar cat alogs. The technique is completely formal and does not require human o perator intervention, hence the prediction results can be objectively tested. Moreover, the maps can be used as the Poisson null hypothesis for testing by the likelihood method against any other prediction mode l which shares the same sample space (the same zones, time window, and acceptance criteria).