Swarm Earthquake Hypocenter Relocation in Ambarawa 22 October – 24 November 2021 using Double Difference Method

The swarm earthquake that occurred in Ambarawa from October 22 to November 24, 2021, was an earthquake with a relatively small magnitude and occurred repeatedly over a certain time span, which is commonly called an earthquake swarm. Disaster mitigation efforts needs to be carried out considering that the area most of the tourist destinations. To assist disaster mitigation efforts, it is necessary to relocate the hypocenter. The relocation of the hypocenter itself aims to obtain an earthquake hypocenter position that has a higher level of accuracy by taking into account the RMS (Root Mean Square) value. The data used in this study is data from the earthquake swarm that occurred in Ambarawa obtained from the Geophysics Station Class I Sleman, Yogyakarta. The method used to relocate in this study is the Double Difference Method using hypoDD software. The purpose of research is to obtain the hypocenter point of the earthquake which is the trigger for the earthquake as a form of disaster mitigation effort. The results is study are changes in the position of the earthquake hypocenter that form clusters in the area around the border of the Ambarawa subdistrict and Banyubiru subdistrict after the relocation. On average, a swarm earthquake occurs at a depth of 0 – 15 km below the surface with an average magnitude ≤ 3 SR and triggered by fault activity around Ambarawa.