Evolution of the stress field in the northern Aegean Sea (Greece)

The evolution of the stress field in the area of the northern Aegean Sea during the 20th century has been studied. The area is dominated by dextral strike-slip faulting and is characterized by frequent strong earthquakes. Coulomb stress changes (Delta CFF) were calculated assuming that earthquakes can be modelled as static dislocations in an elastic half-space, and taking into account both the coseismic slip in large (M greater than or equal to 7.0) earthquakes and the slow tectonic stress build-up along the major fault segments. The stress change calculations were performed for strike-slip faults of strike, dip, and rake appropriate to the large events. We evaluate whether these stress changes brought a given large earthquake closer to, or farther from, failure. It was found that each of the large events occurred in regions of increased calculated Coulomb stress. Moreover, the majority of smaller events for which reliable fault-plane solutions are available were also located in areas of positive Delta CFF. By extending the calculations to 2020, and assuming that no additional large (M greater than or equal to 7.0) earthquake occurs between 1999 and 2020, possible sites of future large earthquakes are identified.