The Purpri Fault: A Newly Identified Active Fault in East Kolaka, Indonesia, Based on HypoDD and DInSAR

Abstract

The Purpri Fault, a newly identified active fault in East Kolaka, Indonesia, has been analyzed using an integrated geophysical approach, combining HypoDD earthquake relocation and DInSAR ground deformation analysis. The relocation of 233 seismic events from January 24 to February 7, 2025, revealed a fault structure distinct from the Middle Kolaka and North Kolaka Faults, characterized by an oblique-normal faulting mechanism with a left-lateral component. The focal mechanism solution confirms significant vertical displacement, indicating a fault that accommodates both extensional and shear deformation. DInSAR analysis using Sentinel-1A SAR imagery detected subsidence and uplift patterns that align with the relocated seismicity, confirming ongoing crustal deformation along the Purpri Fault. The western block of the fault exhibits a subsidence of approximately –13 cm, while the eastern block shows uplift of +11 cm, consistent with the seismic activity. The integration of seismic relocation and deformation mapping interpretation confirms that the Purpri Fault is an independent and active fault system. The shallow depth of seismicity (<10 km) and evidence of ongoing deformation indicate a potential seismic hazard that is not currently accounted for in regional seismic hazard models. Given its capacity to generate moderate to strong earthquakes, incorporating the Purpri Fault into updated seismic risk assessments is essential for improving earthquake preparedness and hazard mitigation strategies in East Kolaka.