Tomography of seismic wave’s velocity structure using swarm earthquake data in Jailolo area, West Halmahera

From the analysis of seismic recording using JISVIEW, from August 12 to September 12 2016, there are 264 earthquakes detected. After running the simultaneous hypocenter relocation and seismic velocity (P waves) tomography inversion, we found 219 earthquakes that can be relocated and used in seismic tomography inversion. From the seismic velocity structures, 3-D slice from various lines (Figure 1), we found a high contrast of P-waves velocity that concentrated in the middle of Jailolo Bay at the depth from 0-8 km, and spreading to the north and south of Jailolo bay (Figure 2) .This high velocity contrast is interpreted as igneous rock from previous eruption in the past. At 15-30 km depth, the high contrast is replaced by low velocity contrast. The low velocity contrast at the depth between 15-30 km is interpreted as magma bodies that pushing igneous rock above its bodies upward. This magmatic activities are assumed as a source of swarm activites at Jailolo and its surrounding areas in 2015.