Constraints on the location of the 2008, Mw6.4 Achaia-Ilia earthquake fault from strong motion data

Περίληψη

The June 2008, Mw6.4 Achaia-Ilia earthquake was the first recorded dextral strikeslip event of considerable magnitude in western Peloponnese, which, nevertheless, could not be related to any of the known/mapped structures at the ground surface. Published locations of the mainshock focus by various agencies/researchers differ by as much as 6 km and 16 km in the horizontal and vertical dimensions, respectively, making even more difficult the accurate siting of the seismogenic fault. However, the 2008 earthquake provided a valuable set of near-fault strong motion data, which could shed some light on the problem of accurately locating the earthquake source. To this end, we use the discrete wavenumber method to forward model the strong ground motion records at three stations, located close to the prolongation of the 2008 strike. We test different locations and lengths for the ruptured plane and compare synthetic polarities and amplitudes of the first strong S-wave pulse to actual data. We conclude that the line of maximum moment release (our fault models are vertical planes) during the 2008 earthquake is located to the east of the imaginary line connecting stations PAT2 and AMAA and to the west of station PYR1.