Aftershock sequences of some large earthquakes in the region of Greece

Deformation characteristics, magnitude and time distributionof the aftershocks of the large earthquakes, occurred in the regionof Greece from 1926 till 1964 are investigated. An approximate relationbetween the number of aftershocks and the magnitude and focal depthof the main shock has been found. Also, an approximate relation has beenderived between the magnitude of the largest aftershock and the magnitudeand focal depth of the main sliok. The largest aftershock occurs withinfourteen days after the main shock. In many cases large " late aftershocks "occur one or more months after the main shock. One or more foreshocksof 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 muchsmaller than the main shock is 10%. It is shown that some properties ofthe Earth's material in the aftershock region can be derived by studying themagnitude distribution and deformation characteristics of the aftershocks.