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Fig. 4
Intensity attenuation
curves. (
a
) all data, (
b
)
perpendicular to the fault
azimuth, (
c
) fault azimuth,
(
d
) based on isoseismals, (
e
)
combined with the geological
cross-section, (
f
)PGA
distance attenuation, (
g
)
PGA-Intensity correlation
level. In this case we use subjectively four categories of site classification which are
related to the lithofacies as shown in the used geological cross section. One may
consider that attributing an amplification value to broad areas such as at the Blida
Mountains is useless.
To determine the contribution of the source of the 2003 earthquake to the seis-
mic hazard, it is essential to estimate how the seismic parameters such as the peak
acceleration or EMS intensity decrease with distance. Our attempt is to use previous
works on the elaboration of an empirical attenuation law for northern Algeria and
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