MICROSEISMICITY AND SEISMOTECTONIC PROPERTIES OF THE LEFKADA – KEFALONIA SEISMIC ZONE

Résumé

Microseismicity, focal–mechanisms, and previously–published focal parameter data are used
to determine the current tectonic activity of the prominent zone of seismicity in Lefkada and Kefalonia
Islands. Recordings from a local network installed and operated on the two Islands, as
well as from permanent stations there, were used to obtain accurate microseismicity locations,
which in turn is exploited to reveal properties of smaller localized active structures and the
large–scale crustal faulting. The microseismicity substantially agrees with the historic seismicity
and delineates a relatively narrow, major zone of activity that extends along the western
coasts of both Islands. Cross sections were used in order to provide a detailed
characterization of the microseismicity and a high–resolution picture of the seismically defined
structures. For the investigation of the past seismic activity relocation of the hypocenters of
older events was performed, using a reliable velocity model and time delays for the regional stations,
calculated on the basis of the accurately determined focal parameters using the local
recordings. The yielding location improvement contributes to the geometry identification of the
active structures, which were previously obscured by location errors, and which constitute a
critical input for the study area seismic hazard assessment.