This research was examines the focal mechanism associated with the mainshock and three aftershocks of the magnitude 6.3 Yogyakarta earthquake on May 27, 2006. This study, therefore, aims to provide a cleareranswer on the source mechanism of the earthquake, which has been debated. Data were obtained from the mainshock and aftershock sources, on June 8, 9, and 16, 2006. The mainshock and three aftershocks were used to conduct waveform inversion by calculating the Green's functions through the extended reflectivity method of the near-field and the far-field signal component. The mainshock's focal mechanism has a strike, dip, and range angle of 243.40o, 77.50o, and -28.30o, respectively.
Furthermore, the mainshock is not a pure strike-slip as previously hypothesized. The focal mechanism for the aftershock earthquake source on Mw 4.4, obtained on June 8, had a strike, dip, rake, and variance of 192.20o, 29.70o, -48.30o and 0.22, respectively. This aftershock had a different segment from the mainshock event and those obtained on the 9 and 16 of June with the same type of faulting as the mainshock with variance values of 0.195 and 0.243. These results showed that the mainshock of May 27, 2006, activated the aftershock on June 8, with a different type of fault.