Earthquake Hazard Modeling in Java Using Space Time Epidemic Type Aftershock Sequence

Appropriate earthquake hazard modeling is important for Indonesia to produce a more accurate earthquake hazard map because Indonesia is one of the most vulnerable countries for earthquake occurrence, especially Java region which is considered as the most populated region. However, previous study cannot perform analysis for complete earthquake catalog data in Indonesia because it requires complex model with a number of parameters and computationally expensive approach. In this study, we perform earthquake analysis using the space-time epidemic type aftershock sequence (space-time ETAS) in Java occurred during 1 January 2003 to 30 June 2023 with magnitude greater than 4 and depth less than 300 km. We consider the combination of Davidon-Fletcher-Powell and stochastic declustering algorithms to obtain a scalable procedure. The results show that Java has a low earthquake rate, i.e. less than 0.1 events/day.deg2, and a moderate clustering coefficient. This research provides information that the number of earthquakes in Java is relatively small and is not significantly influenced by the occurrence time of the main earthquake.