Detailed seismotectonic investigation of the broader Aegean region using digital seismological data

The present PhD thesis focuses on the characteristics of the natural processes taking place at the source of the earthquakes through the study of the focal mechanisms, the slip distribution and the characteristics of the earthquake sequences of the broader Aegean region. In Chapter 1 a review of the current kinematic models for the broader Aegean region is presented along with information regarding the physical characteristics of the crust and uppermost mantle. In this chapter also the velocity vectors derived from GPS campaigns from various authors are combined in addition to the slip vectors calculated from the focal mechanism of strong earthquakes for which the fault plane is known. In Chapter 2 the theory of the Moment Tensor is presented, together with the methods for its decomposition and information regarding the inversion process. The process of the construction of Green’s function is analyzed, different velocity models are presented and tested and follows a discussion regarding the uncertainties of the inversion procedure. Chapter 3 includes the results of the epicenter and focal mechanism analysis of the seismic sequences of Skyros (2001), Vartholomio (2002), Psaxnon (2003), Saros (2003), Lefkada (2003), Loutron-Alexandroupolis (2004) and of the Sigaçik Gulf in Turkey (2005). In the current chapter the “quick focal mechanism” determination from the Geophysical Laboratory is presented along with a preliminary comparison of the results with those of International Seismological Institutes. -330- In Chapter 4 the inversion method for the calculation of the slip distribution on the fault plane using teleseismic data is presented. The method has been applied to the earthquakes: Montenegro mainshock (1979), Montenegro largest aftershock (1979), Lefkada (2003), Sigaçik (2005), Kythera (2006). Also it was performed a detailed sensitivity analysis of the inversion method in order to reveal its uncertainties and resolution. In this chapter the effect of directivity of the earthquakes is also analyzed, the Empirical Green’s Function method and the inversion of the Source Time Function for the retrieval of the slip on the fault plane. Chapter 5 describes the way towards a realistic calculation of the ground motion from slip distribution models. Examples from the Montenegro events and Lefkada mainshock are presented and a discussion on the quality of the results is made. Chapter 6 hosts the conclusions of the present dissertation and a discussion of the geotectonic characteristics of the Aegean region.