Aftershock sequences of some large earthquakes in the region of Greece

Deformation characteristics, magnitude and time distribution of the aftershocks of the large earthquakes, occurred in the region of Greece from 1926 till 1964 are investigated. An approximate relation between the number of aftershocks and the magnitude and focal depth of the main shock has been found. Also, an approximate relation has been derived between the magnitude of the largest aftershock and the magnitude and focal depth of the main sliok. The largest aftershock occurs within fourteen days after the main shock. In many cases large " late aftershocks " occur one or more months after the main shock. One or more foreshocks of magnitude larger than 3.5 occurred in forty per cent of the cases. The probability for an earthquake to be preceded l>y a large foreshoek not much smaller than the main shock is 10%. It is shown that some properties of the Earth's material in the aftershock region can be derived by studying the magnitude distribution and deformation characteristics of the aftershocks.