Source mechanism identification using regional waveform inversion approach, case study: July 7, 2019 Molucca Sea earthquake

Abstract

Molucca Sea is a seismically active area in eastern Indonesia. An earthquake occurred near to Ternate City, Province of North Maluku (M6.8: depth 29 km) on July 7, 2019. To investigate the detail about the mechanism of the earthquake, we analyzed the moment tensor of the earthquake by applying the regional waveform inversion. We used three components waveform broadband data from 18 station of IA-net seismic network in this study. We carried out the deviatoric mode to determine the double couple and compensated linear vector dipole (CLVD) component of the earthquake. The position and origin time of the earthquake were calculated by a space-time grid search in vertical and lateral positions. The frequency band of 0.01 – 0.023 Hz is used in the inversion process to reduce the instrument low-frequency disturbance and the effect of inaccurate velocity model for the synthetic seismogram. The moment tensor inversion result shows that the source mechanism of the earthquake is transpressional fault. This result agrees well with the tectonic setting of the study area.