Hypocenter relocation along the sunda arc in Indonesia, using a 3D seismic-velocity model

The tectonics of the Sunda arc region is characterized by the junction of the Eurasian and Indo-Australian tectonic plates, causing complex dynamics to take place. High-seismicity rates in the Indonesian region occur due to the interaction between these tectonic plates. The availability of a denser network of seismometers after the earthquakes of Mw 9.1 in 2004 and Mw 8.6 in 2005 supports various seismic studies, one of which regards the precise relocation of the hypocenters. In this study, hypocenter relocation was performed using a teleseismic double-difference (DD) relocation method (teletomoDD) combining arrival times of P and S waves from stations at local, regional, and teleseismic distances. The catalog data were taken from the Agency of Meteorology, Climatology, and Geophysics (BMKG) of Indonesia, and the International Seismological Centre (ISC) for the time period of April 2009 toMay 2015. The 3D seismic-wave velocity model with a grid size 1° × 1° was used in the travel-time calculations. Relocation results show a reduction in travel-time residuals compared with the initial locations. The relocation results better illuminate subducted slabs and active faults in the region such as the Mentawai back thrust and the outer rise in the subduction zone south of Java. Focal mechanisms from the Global Centroid Moment Tensor catalog are analyzed in conjunction with the relocation results, and our synthesis of the results provides further insight into seismogenesis in the region.