HR: 1340h
AN: S13B-0208    [Abstracts]
TI: The Athens 7-9-1999 Earthquake and its post Event Activity as Recorded by a Local Seismic Array
AU: Makris, J N
EM: info@geopro.com
AF: GeoPro GmbH, St. Anneufer 2, Hamburg, GER 20457 Germany
AU: * Papoulia, J E
EM: nana@ath.hcmr.gr
AF: Institute of Oceanography, Hellenic Centre for Marine Research, 46,7 Km Athinon Souniou, Attiki, Anavissos, GR 19014 Greece
AU: Stavrakakis, G N
EM: stavr@gein.noa.gr
AF: Geodynamic Institute, National Observatory of Athens, Lofos Nymfon, Thissio, Athens, GR 11810 Greece
AB: The 7-9-1999 Ms5.9 Athens Earthquake was the most destructive event ever reported in the modern Greek history, causing 143 human losses and an enormous material damage. In order to understand the mechanism of this unexpected event that occurred in an area defined by the Greek seismic code as a zone of low seismic hazard, we deployed a dense network of 20 seismic stations to observe the post event activity for a period of two months. The recorded microseismicity exceeded 4000 events. These were located within a triangular zone that is intersected at its eastern margin by the large tectonic boundary between the metamorphic units of Penteli - Immitos to the southeast and the less metamorphic units of Parnitha to the northwest. The northern boundary of this zone strikes E-W, extending for more than 20 Km between Kithaeron and Penteli mountains, along the Fili fault. The located hypocenters increase in depth from about 5 Km beneath the Parnitha mountain and 20 Km below the island of Salamis. The southwestern boundary of this triangular zone terminates along the Thriassion fault of NW-SE orientation. The stress field that triggerred the seismic deformation is associated with the rapidly developing extensional processes in the gulf of Corinth. This is justified by solutions of the focal mechanism showing a pure extensional process along an E-W oriented listric fault gradually dipping to the south. Five years after the occurrence of the 5.9 event the area of Parnitha is still seismically active as shown by later installed local arrays. The fact that the main energy was released in 1999 by the 5.9 event and a few large aftershocks and since then it is continuously dissepating by microearthquakes supports the assumption that the seismic risk from this area for the city of Athens is at present negligible.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1217 Time variable gravity (7223, 7230)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005