The evaluation of the parameters c and k of the decay law of the aftershocks in an earthquake sequence has been carried out in this study. For this reason 170 seismic sequences globally distributed, during the time period 1964-1986, were performed. All of them modelled well by Omori’s law. We estimated that the mean global values of and parameters , are 0.660+0.181 and 0.341+0.090, respectively. The values of these parameters are also estimated for different regions of the world, west and east part of circum-Pacific rim, as well as for the Eurasia belt.The parameters c and k calculated for the various regions of the world found to be spread around the global average, although admittedly few exceptions to this generalization are also observed to exist.

The October 2005 series of earthquakes that occurred in the Gulf of Sigacik (western Turkey) reveal the operation of pure strike-slip faults, as evidenced from the 49 focal mechanisms we determined, in a region dominated by N-S extension and bounded by well-documented graben structures. The sequence is characterized by the occurrence of three moderate size events (17 October 2005, 05:45 UTC, Mw 5.4; 17 October 2005, 09:46 UTC, Mw 5.8; and 20 October 2005, 21:40 UTC, Mw 5.8) with an eastward propagation and close spatial separation (< 6 km). We relocated over 200 aftershocks, combining phases from the Greek and Turkish seismological networks, which align roughly in a NE-SW cloud, but considerably spread after the first day of the sequence, indicating the simultaneous activation of multiple structures nearly orthogonal to the main rupture. It is hard to relate the occurrence of the events to any of the previously mapped faults in the region. The region of occurrence is a well-known geothermal area which implies that it is in a very unstable state, with the fault systems close to rupture and very sensitive to stress perturbations. Here we showed that the sequence is adequately explained by static stress triggering. It is worth noting that this sequence, though moderate in magnitudes, provides stronger evidence for the operation of sub-parallel strike-slip faults in the central Aegean Sea-western Turkey, north of the volcanic arc, which seem to be optimally oriented in the regional stress field and facilitate the Anatolia motion into the Aegean Sea. (c) 2006 Elsevier B.V. All rights reserved.

The Parnitha mountain range lies between two Quaternary rift systems in central Greece: the Gulf of Corinth Rift and the Gulf of Evia rift. We suggest that the range was formed by footwall uplift on active normal faults striking WNW–ESE and NE–SW. We investigated the scarp appearance, geometry and slip rates of three normal faults bounding this mountain range by field mapping at 1:5000 scale. Active faults studied include the 8.5 km long Fili Fault, the 4.7 km long Maliza Fault and the 4 km long Thrakomakedones Fault. We calculated comparable mean slip rates for all mapped faults (Fili: 0.18 mm/yr, Avlon: 0.2 mm/yr, Thrakomakedones: 0.24 mm/yr); however, we suggest that the WNW–ESE structures are more active during the Late Quaternary because of abundant field evidence of recent movements along slip surfaces (fresh basal stripes and slickenlines). In addition, stress axes analysis shows a N7°E–N25°E (NNE–SSW) oriented, extensional stress field, which is compatible with the focal mechanism of the Athens 1999 earthquake. The fault-slip data from the Parnitha faults show orientations similar to other low-strain areas in central Greece, such as the Gulf of Evia Rift to the north. Our slip rate estimates may explain the low recurrence of large earthquakes in Attica as opposed to high slip rate areas in central Greece such as the neighbouring Gulf of Corinth.

The rupture zone of the M-W 6.5 earthquake of 26 July 2001 in the North Aegean Sea (NAS) is oriented northwest-southeast and occupies the southwestern part of the seismic zone of NAS. The motion indicates reverse faulting with a significant sinistral strike-slip component. A review of the past NAS seismicity reveals that in the last 150 yr the seismicity is strongly clustered in time with 14 out of 15 pre-2001 events being members of a cluster. Only the 1912 earthquake is an isolated event. This implies that the probability of the 2001 earthquake being the first member of a new time cluster is 0.93, which is the probability for the next NAS strong, earthquake to occur within a time interval equal to the mean interarrival time of cluster events: 2.9 +/- 2.06 yr. The distribution of the earthquake rupture zones and the position of the 2001 event suggest that the next event may rupture one of the unruptured parts of NAS to the northeast of the 2001 earthquake.

We improve the historical earthquake catalogue of the south Ionian Sea by critically reviewing twelve earthquake events occurring in the time interval 1591-1837. For some of them we complete historical information while for others we present information not taken into account in previous seismological studies. The procedure of réévaluation concluded with significant results. For example, the 5 May 1622 earthquake in Zakynthos , considered so far as a large destructive event, proved to have been only a felt event without any destructive effects, while the strong shocks of 21 August 1591 and 28 October 1766 (O.S.) are new events in the seismological literature. Tsunami phenomena reported in association with particular earthquakes also were reevaluated. It is shown that the large earthquake of 29 December 1820 in Zakynthos was not followed by a destructive tsunami flooding, as thought by previous authors, while evidence is presented that the sea-wave reportedly occurring in the Corinth Gulf in association with an aftershock of the above earthquake on 6 January 1821 very likely was not a tsunami but a storm surge that attacked the coast of Patras. The results obtained are of importance for the seismic and tsunami hazards assessment in the Ionian Sea.

Foreshock activity preceding strong (Ms ≥ 5) main shocks in the Corinthos Gulf, Central Greece, is examined from primarily a data set of 1970–1998 and supplementary from data sets of 1785–1910 and 1911–1969. It has been found that foreshock activity appears at time T ≤ 4 months before the main shock. In general there is no apparent tendency of foreshock epicenters to move towards the main shock epicenter. The last 10 days of the foreshock period is the most important phase since the probability for the main shock occurrence at any time within that time window is very high exceeding 0.83. The duration of the foreshock period as well as the largest foreshock magnitude are both independent of the main shock magnitude. Obtained results are important for inclusion in probabilistic earthquake predictions in the Corinthos Gulf.