Spatio-temporal Hazard Earthquake Modeling in Java Using Space-time Epidemic-Type Aftershock Sequence (ETAS)

The Space-Time ETAS (Epidemic-Type Aftershock Sequence) model is a point process-based approach for earthquake modeling that utilizes comprehensive seismic catalogs to forecast earthquake occurrences by accounting for both spatial and temporal relationships. It employs a long-decay spatial density function, which represents the gradual reduction in the probability of aftershocks as the distance from the main shocks increases. However, the Java region, characterized by complex tectonic interactions and the Andaman-Sumatera-Java arcs subduction zone, experiences deep and spread earthquakes, exhibit spread earthquakes along its subduction zone, which may suggest an alternative spatial density function within the Space-Time ETAS model. This study compares the commonly used long decay and short decay spatial density in the Space-Time ETAS model to fit the earthquake catalog in Java based on model complexity, computational time, and intensity prediction. The dataset includes earthquake catalog data (longitude, lattitute, time occurrence, magnitude) in Java within interval time 1 January 2009 to 31 January 2025. Findings reveal that the short-decay function outperforms the long-decay counterpart, efficiently identifying high-seismicity areas in the Andaman-Sumatera-Java arcs and 36 active faults. This study advances seismic risk assessment and supports disaster mitigation efforts in Java.