Aftershock location determination of the 27 May 2006, M 6.4 Yogyakarta earthquake using a non-linear algorithm: A preliminary results

Abstract

The Special Region of Yogyakarta has experienced a fairly high seismic activity due to its location in an active tectonic setting. One of the active fault in this region is the Opak fault which has striking south west - north east. In this study, we analyzed aftershocks sequence through waveform data which taken from 16 temporary GeoForschungsZentrum (GFZ) network stasiuns located around the Opak fault. We selected the event from the waveform which have (time difference between S-and P-wave arrival time) ts−tp< 7 second, and have picked carefully manually by eye the arrival times of the aftershock in the period of 3 June to 6 June 2006. For determining the aftershock hypocenter location, we used the non-linear algorithm of NonLinLoc program. Our results show distribution of aftershocks are located about 5-15 km further to the east from the Opak fault and the cluster of the aftershock hypocenter is situated close to USGS mainshock hypocenter. Later on, for giving better understanding the indication of connection betwen Opak fault and Yogyakarta earthquake, we have been conducting tomographic inversion to determine 3-D seismic velocity structure in the region.