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The Mw7.4 Izmit earthquake of 17 August 1999 struck a part ofthe North Anatolian fault in the area of Izmit Bay (NW Turkey). Historicalinformation shows that the fault which moved during the generation of thisearthquake consists of two fault segments moved during the generation oflarge (M ∼ 7) earthquakes in 1719 and 1754, respectively. Since then onlythe central part (between Izmit and Lake Sapanca) of this fault ruptured bythe generation of a smaller shock (M = 6.6) in 1878.The spatial stress variations based on the calculation of changes in theCoulomb Failure Function (ΔCFF) associated with this earthquake aresupported by the distribution of strong aftershock foci. Large positive valuesof ΔCFF to the east and west of the mainshock epicenter are inagreement with the notion that secondary faults were triggered there by thegeneration of the main event. Large positive values of ΔCFF are alsoobserved in the adjacent western fault segment where the 1766 event wasgenerated, evidencing the occurrence of the next strong earthquake in thissegment.

The test and application of the time and magnitude predictable model in the subduction zones around the circum-Pacific belt is performed. Each subduction zone was separated in several seismogenic regions on the basis of tectonic and geometrical features of the subducting lithosphere and for three different depth ranges. The data derived from these seismogenic regions were used in order to check the suitability of the regional time and magnitude predictable model, as this model was defined for shallow events. The results obtained in the present study confirm that this model appropriately describes the behavior of deep seismicity in these regions, since a positive (c̄=0.31±0.003)and a negative (C̄=−0.13±0.047)dependence were found for the logarithm of the interevent times and the magnitude of following mainshock, respectively, on the magnitude of the preceding mainshock. Moreover, the slip-predictable model was rejected, since a negative dependence was found (Ē=−0.19)between the interevent times and the magnitudes of the following mainshock. Probabilities of occurrence of the future strong (M≥7.0) events in each seismogenic region have been determined for the next decade conditioned on the previous occurrence of such events. The magnitudes of the expected events have also been estimated. Statistical tests for the estimated probabilities exhibit a good correlation with the occurrence rate of such events. Furthermore, the statistical significance of the model has been studied through additional tests. The results of this study demonstrate the validity of the regional time and magnitude predictable model in the areas examined.

The parameter bof the frequency-magnitude relation has been accurately calculated for each of the 21 seismic zones into which the Aegean and surrounding area (34°N–43°N, 18°E–30°E) has been divided on the basis of several seismotectonic criteria. These 21 seismic zones have been geographically separated into three (A, B, C) groups (regions), according to the values of the parameter b. The outer region (A) is characterized by a relatively high value (= 1.03) the middle region (B) by an intermediate value (= 0.84) and the innermost region (C) by a low value (= 0.60). The boundaries of these three groups of zones almost coincide with the boundaries of well-known geological zones. This observation is interpreted in terms of mechanical heterogeneity of the material, and of structural and stress conditions in the area.