The Greek Seismological Institutions, in a synthetic work, compiled the
seismic hazard map for Greece by using all the available seismic data and by
applying different methods. Every Institute computed the expected strong
ground motion at a mesh of grid points and the average values were finally
obtained.

According to this Seismic Code, which is now in operation, Greece is
separated in four categories (I, II, III, IV) of seismic hazard. The IV zone
is considered as the most hazardanous while I as the less one.

The area of Helmos belongs to the III seismic zone for which the most
probable maximum value of peak acceleration am is given by the formula:
logam = 0.264logTm + 1.739.
Thus it is possible on the basis of the classification of a site and the
above relation to determine the value of the seismic motion for any return
period. So for the Helmos area and for 50 yrs return period the value of am
= 0.15 g could be obtained.
It is important to add, that in the Seismic Code, the final adopted values
of am are about the 80% of those calculated by the above formula.


Concerning the maximum acceleration values recorded in the city of Aegion,
during the last disastrous earthquake of June 15, 1995, Ms=6.1, MM=VIII,
are:
<P>
Component             g<br>
Long                      0.492<br>
Tran                      0.533<br>
Vert                       0.193<P>

The instrument was at an epicentral distance of 15 Km. This earthquake was
characterized by strong directivity towards the city of Aegion.
The distance between the site of the astronomical station and the city of
Aegion is about 30 km to the north.

<br>
Dimitris Papanastassiou<br>
National Observatory of Athens<br>
Institute of Geodynamics<br>
P.O Box 20048<br>
11810 Athens<br>
Tel +3013490195<br>
Fax+3013490180<br>
e-mail:d.papan@gein.noa.gr<br>