Recent earthquake activity in Trichonis region and its tectonic significance



SUMMARY. - The aftershock activity associated with the central Greece
(Trichonis Lake) earthquake of |une-Dec. 1975, has been studied, with emphasis
on the time and magnitude distribution. It has been found that the value of b,
in Gutenberg - R i c h t e r ' s relationship was near the same for the primary as
well as the secondary or second order aftershocks of the sequences, but depends
upon the focal depth.
A correlation between the calculated focal mechanisms and the associated
stress components to the distribution pattern of meizoseismic effects as well
as to the geological structure of the seismic region was found.
The seismic region lies at the top of an anticline which was found moving
downwards, apparently due to compressional stresses.
Within the series of three earthquakes the progress of the destruction of
the buildings was observed and reported. The interest is concentrated to modern
buildings out of reinforced concrete and infill brick walls. The relatively unexpected
rather bad performance of the later case of buildings was compared to that
of the traditional small houses out of brick or stone masonry, the behaviour of
which may be considered as better from what it was expected.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X