Rupture Directivity During the September 7, 1999 (Mw5.9) Athens (Greece) Earthquake Inferred from Forward Modeling of Strong Ground Motion

The empirical Green’s functions technique is applied to simulate strong ground motion records from the September 7, 1999, Athens earthquake. Information on the fault parameters from previous independent studies has been used and several scenarios were examined, in regard to the location of the starting point of the rupture, by comparing the synthetic records with the corresponding observed ones, through a residual function and a correlation function. The results show that the rupture started at the deepest, 4–5 km, part of the fault from its western edge. This hypocenter was then used, in combination with the initial fault model, to stochastically simulate the strong ground motion during the Athens main shock, in terms of peak-ground acceleration at hard rock. The results show that directivity might have significantly contributed to the destructiveness of this earthquake at specific parts of the Athens Metropolitan area.