|
|
||||||||
Article |
Department of Geophysics
Aristotle University of Thessaloniki
54124 Thessaloniki, Greece
(Z.R., A.K.)
Institute of Engineering Seismology and Earthquake
Engineering
P.O. Box 53
55102 Thessaloniki, Greece
(N.T.)
The stochastic method for finite faults is applied to simulate strong
ground motion from the 7 September 1999, moment magnitude M 5.9 Athens
earthquake. The method includes descritization of the fault plane into a
certain number of subfaults, each of which is assigned an
-2 spectrum. A slip-distribution model, derived
from previous studies of this earthquake, is used to specifically account for
the source effect. Contributions from all subfaults are then empirically
attenuated to the observation sites, where they are summed to produce the
synthetic acceleration time history. The method is first calibrated against
its ability of reproducing the recordings at 19 strong-motion stations, at
epicentral distances ranging from 16 to 61 km. The calibrated model is then
applied to calculate synthetics at a large number of grid points covering the
area around the fault plane. Simulated peak values are subsequently used to
produce synthetic peak ground acceleration and spectral acceleration maps at
hard rock. Both peak ground acceleration and spectral acceleration maps imply
energy directivity toward the east, where most of the damage was concentrated.
The directivity effect is most prominent at large periods (>2 sec) and in
the period range 0.2 to 0.3 sec. Independent geotechnical studies showed
considerable site effect at periods <0.5 sec within the meizoseismal area.
This result, coupled with the results of the present study, imply that the
damage distribution pattern of the 1999 Athens earthquake can be explained by
the destructive combination of two factors: the source directivity and the
site effect.
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |