Teleseismic Double-Difference Earthquake Hypocenter Relocation in the Indonesian Region

Accuracy of hypocenter location is a crucial obstacle for seismicity study. Therefore, it is important to obtain accurate earthquake location using an adequate relocation method. We have relocated nearly 30,000 earthquakes (with magnitude greater than 2.0) compiled by BMKG from April 2009 to June 2014 around the Indonesian region using teleseismic double-difference relocation algorithm. We used arrival time data from local, regional and teleseismic stations. For the inversion procedure, we have applied 1-D and 3-D seismic velocity models to determine earthquake hypocenter location. Our relocation results show that the travel-time RMS errors were greatly reduced. The hypocenter locations distribution shows significantly improved locations after the relocation. The relocated hypocenters also exhibit improvement in hypocenter depths particularly for shallow earthquakes. Overall, our relocation results were well correlated with tectonic features in this region, e.g. major subduction zones beneath Sumatra, Java, Bali, Banda, Sulawesi and Molluca and inland fault zones such as the Sumatra faut zone. These results will provide better information for updating seismic hazard maps and further advanced studies in the Indonesian region.