Geodetic slip rate and seismogenic depth of unmapped active faults in Yogyakarta, Indonesia, inferred from dense Global Navigation Satellite System campaign observation

Yogyakarta was struck by a devastating M W 6.3 earthquake, which intensified awareness about the seismic hazards in the region. This study investigates the kinematic slip rate and seismogenic depth of the northern segment of Opak Fault and an unmapped fault known as Ngalang Fault in Yogyakarta, utilizing Global Navigation Satellite System (GNSS) data collected between 2019 and 2023. By deploying a network of 12 GNSS stations alongside continuous observations from the InaCORS network, we performed a detailed geodetic analysis to discern current deformation patterns. To quantify the slip rate, we established a frame of reference using the Sundaland Block’s rotational parameters and applied the Euler pole angular velocity to transform daily GNSS solutions accordingly. The findings reveal significant left-lateral strike-slip motion in the northern segment of Opak Fault, with a slip rate averaging 3 mm/yr and a locking depth of 2.1 km in Northern Segment, whereas the slip rate averages 1.1 mm/yr and the locking depth is estimated at 1 km in the Ngalang Fault, indicating active geological movements that may influence future seismicity.