On certain aftershock and foreshock parameters in the area of Greece

B. C. PAPAZACHOS

Abstract


Published information (l2) on the aftershocks and foreshocks
of many principal shallow earthquakes occurred in the area of Greece
between 1911 and 1973 constitutes a more or less homogeneous and complete
sample of data in respect to some properties of these seismic sequences.
These data have been used to determine certain parameters of these sequences.
The value of the decay parameter p, in the time distribution law of
aftershocks, is independent of the magnitude range and varies between 0.7
and 1.9 in this area. The smallest value was found for the aftershock sequence
of an earthquake believed to be associated with the Kremasta artificial
lake, while the largest value was found for the aftershock sequence of
an earthquake occurred in the volcanic part of the Hellenic arc. The probability,
N, that the largest aftershock will occur Tl days after the main shock
or later is given by a relation of the form N = c — k log Tl.
Representative values of the parameter b, in the frequency-magnitude
relation, have been found for the foreshocks as well as for the aftershocks of
the same main shocks, by a proper grouping of the data. This value is
equal to 0.67 for foresliocks and equal to 0.92 for the corresponding aftershocks.
The difference in magnitude between the main shock and the largest aftershock
is almost independent of the magnitude of the main shock. The relation
M0 — = 1.1 holds on an average.

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References


DOI: https://doi.org/10.4401/ag-4935
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X