ACTIVE ZONE SIZE VERSUS ACTIVITY - STUDY OF DIFFERENT SEISMICITY PATTERNS IN THE CONTEXT OF THE PREDICTION ALGORITHM M8

A new precursory measure called active zone size (AZS), based on the d evelopment of spatial correlations, was recently introduced in the con text of predicting large events in dynamical models of faults. The new measure counts the fraction of the total seismic area which has exhib ited earthquakes recently. In each of the models tested, AZS was found to be more strongly correlated with an increase in the likelihood of a large event than the more conventional measure activity (N), which i s defined to be the total number of earthquakes, In this paper we repo rt the first application of AZS to seismicity catalogs. We compare mea surements of AZS and N both individually and in the context of the int ermediate-term earthquake prediction algorithm M8 applied here specifi cally to data from the western United States. To test the performance we replace functions in M8 which are based on N with similar functions based on AZS. When this is done, at least on this limited data set, t he performance of M8 is somewhat improved: false alarm time is reduced , and the Landers earthquake is successfully predicted.