Christoforos Benetatos

Complex and segmented rupture associated with the 14 August 2003 Mw 6.2 Lefkada, Ionian Islands, earthquake

The 14 August 2003 (M w 6.2) Lefkada earthquake ruptured the Lefkada Segment of the Cephalonia transform fault zone (CTFZ), a major structure along the Ionian Islands of Greece. We invert 30 P and 9 S waves recorded by the Global Seismographic Network to recover the slip distribution on the fault. Teleseismic (Benetatos et al., 2005) and regional (Zahradnik et al., 2005) waveform modeling has revealed the multiple-event (mainly double) character of the mainshock. Our slip model indicates that the earthquake did occur as two distinct subevents, separated in space by approximately 40 km and in time by 14 sec. The two subevents ruptured the Lefkada segment of CTFZ. Rupture initiated in the north and propagated to the south with an average speed of 2.4 km/sec. The moment was released in three distinct patches. The first patch of moment release, located beneath the western coast of Lefkada Island, is confined in a small area (� 25 10 km 2 ), extends in depth from 10 to 25 km, and here the maximum slip of � 34cm is observed. The second patch of moment release is located offshore further to the south, but close to the northern coast of Cephalonia Island, and is confined in an even smaller area (� 15 10 km 2 ). The third patch, for which the uncertainty is the highest, occurred at the intersection of the two fault segments, which is actually the intersection of the Lefkada and Cephalonia segments of the CTFZ. To obtain a satisfactory fit to the regional and teleseismic body waves the contribution from subevents on both segments has to be considered. An extensive sensitivity analysis is performed to quantify the uncertainty of the slip model. ShakeMaps of peak ground velocities, simulated from the slip model, are found to be in good agreement with the distribution of reported damage and intensity level of VII, at the regions near the epicenter and especially on the western coast of Lefkada Island.