Refining the Regional Aftershocks Catalog of the Ambon Earthquake Mw 6.5 on 26 September 2019 using manual picking and a non-linear algorithm: Preliminary Result

Abstract

Abstract A destructive earthquake with magnitude Mw 6.5 occurred in Ambon, Indonesia, on 26 September 2019. This earthquake generated an aftershock sequence. In this study, we determined the location of the aftershock sequence using a non-linear algorithm from the Non-Linear Location (NonLinLoc) program. The catalog and waveform data were collected using 11 seismographs from BMKG regional network located around the Maluku archipelago. The data was recorded between 26 September and 18 October 2019. We have manually picked the P-and-S wave phase by using Seisgram2K software. In our preliminary result, we have located about 1,300 events of aftershock sequence with about 8,500 phases of P and S waves. Overall, the location of the focus depth of the aftershock sequence is dominantly distributed in between 5 - 25 km. Approximately ~70% of the distribution of aftershock locations show a North-South (N-S) oriented pattern from west Seram to Ambon Islands. Meanwhile, about ~20% of the aftershock’s locations are distributed around Ambon Island. Our ongoing and future study is to determine accurate hypocentre location derived from double-difference hypocenter relocation with waveform cross-correlation.