Updating Hypocenter Relocation in Indonesia using 3D Seismic Velocity Model: Period of April 2009-March 2018

In the past 2 years, we have been conducting routine hypocenter relocation in Indonesia. We compiled and conducted hypocenter relocation of ∼50.000 events from a magnitude of 1.4 to 8.5 recorded by 451 stations around and outside Indonesia region. We used local, regional, and teleseismic arrival time data from Indonesian Agency of Meteorology, Climatology, and Geophysics (BMKG) catalog from April 2009 to March 2018. We performed teleseismic double-difference relocation inversion using our previous study of 3D seismic velocity model beneath the Indonesian region with grid size 1∘ by 1∘ for inside Indonesia region and 1D global seismic velocity model from AK135 for outside Indonesia region. This method improved limitation from BMKG earthquake data catalog in which events were recorded from scattered seismic station array and insufficient azimuthal gap around Indonesia. Our results show that travel-time RMS residuals were greatly reduced compared to those of the BMKG catalog and the hypocenter location shows significant improvement, refining to the geological structure, especially trench and major faults. These hypocenter relocation results can be helpful for another seismic study in Indonesia region that required a precise hypocenter location e.g. body wave tomography and probability seismic hazard analysis.