Analyzing Seismicity Pattern of the Gorontalo Region and Its Surroundings in the Form of Hypocenter Relocation Using Double Difference Method

The level of seismic activity due to earthquake events in Gorontalo is strongly influenced by the tectonic system model of the Gorontalo region and the presence of a subduction zone in the Sulawesi Sea. These characteristics make the Gorontalo region have high seismic activity. To describe the pattern of seismicity in the Gorontalo region, it is necessary to conduct an analysis in the form of earthquake hypocenter relocation using the double difference (hypoDD) method. This method uses residual travel time data from each pair of hypocenters to the recording station. This study aims to analyze the results of hypocenter relocation and describe the subsurface model related to the seismicity pattern of Gorontalo and its surroundings. The data used are P and S waves for 7 years recorded at the Meteorology, Climatology and Geophysics Agency (BMKG) station. The earthquake hypocenters relocated in this study were 3,940 out of 4,598 earthquake events. The results of hypocenter relocation show a fairly good seismicity pattern obtained from good RMS values and distribution patterns following Gorontalo tectonic patterns. In general, the seismicity pattern of Gorontalo and its surroundings is strongly influenced by activity in the Sulawesi Sea subduction zone and the Gorontalo fault in the region. The seismicity caused by the subduction zone has a depth of 50 - 200 km, and due to the active faults in the Gorontalo region has a depth of 2 - 25 km.