A study of the 2 December 2002 ( M5.5) Vartholomio (western Peloponnese, Greece) earthquake and of its largest aftershocks

Abstract

Broadband data from the Greek National Seismological Network are used to study the moderate size ( M5.5) earthquake, which occurred on 2 December 2002 near the town of Vartholomio, in western Peloponnese (Greece). Time domain moment tensor inversion applied to retrieve the focal mechanism of the mainshock and of three of the larger aftershocks of the sequence, revealed almost pure strike-slip faulting along NW–SE or NE–SW trending nodal planes. The relative source time functions for the mainshock, obtained from an empirical Green's function analysis, do not reveal any clear directivity to any of the stations. A careful observer might suggest directivity towards NW, if any. Optimum values are 0.4 s for the rise time and 2.7 km/s for the rupture velocity. The spatial and temporal distribution of fault slip showed that the major part of the resolved slip occurred beneath the mainshock's epicenter, ~20 km underneath the western coast of Peloponnese. This probably accounts for the considerable damage observed to the nearby towns. The resolution between the two nodal planes does not permit an identification of the fault plane; however the statistics on the slip distribution model, the preliminary analysis of aftershock locations and macroseismic data favour the NW–SE trending plane as the fault plane, which is connected with sinistral strike-slip motions. These are the first implications for sinistral strike-slip motions in this area and more data are needed in the future to get more reliable resolution of the motions.