Supervisors info:
Γεώργιος Καβύρης, Αναπληρωτής Καθηγητής Σεισμολογίας - Σεισμικής Ανισοτροπίας, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Σχολή Θετικών Επιστημών
Summary:
The northern Gulf of Evia is a graben located in the eastern part of central Greece and is tectonically affected by two stress fields, one in a NE-SW and the other in a WNW-ESE direction. It is, therefore, characterized by a rather complex tectonic system. The area has been affected by several catastrophic earthquakes since the antiquity. The most recent destructive events were two earthquakes that occurred in April 1894. After these events, the Gulf of Evia was not related with large earthquakes.
In November 2014, the area of the northern Gulf of Evia was struck by two shallow earthquakes, followed by a rich aftershock sequence until January 2015. In addition, on June 9, 2015, another large earthquake occurred in the same area.
An upper crust seismic anisotropy study was performed via shear-wave splitting for the above seismic sequence. More specifically, the following parameters were calculated: the polarization direction of the fast shear-wave, the time-delay between the two split shear-waves and the polarization direction of the source. In the present study, a total of 157 earthquakes which were recorded by 4 local stations installed to study the seismic sequence, were analyzed. All results are presented using rose diagrams and equal-area projections. The existence of an anisotropic layer was observed in the northern Evian Gulf, which is in agreement with the strike of the local faults of the wider area and the stress field.
Keywords:
Gulf of Evia, seismic anisotropy, shear-wave splitting, seismicity
