Seismic Activity in Southeastern Mindanao, Philippines

The Davao Region of southeastern Mindanao lies within one of the most tectonically active zones on Earth. This area experiences frequent moderate to large earthquakes due to the complex interactions among the Philippine Sea Plate, the Eurasian Plate, and smaller crustal blocks. Subduction along nearby trenches and strike-slip motion along the Philippine Fault system drive the regional seismicity. Depths of events commonly range from shallow crustal levels to intermediate depths exceeding 50 km, reflecting both interplate and intraplate deformation. On 11 August 2021 at 17:46 local time, a magnitude 7.1 earthquake struck 60 km ENE of Pondaguitan at a depth of 55.1 km. The event originated within the subducting slab, producing strong ground shaking across parts of Davao Oriental and surrounding provinces. No surface rupture was reported, consistent with the intermediate focal depth. Instrumental records since 2000 document several other significant earthquakes within roughly 100 km of this epicenter. A magnitude 7.4 event occurred on 10 October 2025, centered 12 km east of Santiago and approximately 90 km from the 2021 Pondaguitan shock. Earlier, a magnitude 7.0 earthquake took place on 29 December 2018, located 96 km ESE of Pondaguitan. The largest event in the series was the magnitude 7.5 earthquake of 1 January 2001, situated 21 km southeast of Lukatan and 49 km from the 2021 epicenter. These shocks illustrate the persistent seismic hazard along the eastern Mindanao margin. Historical patterns show that intermediate-depth earthquakes in this region often produce felt intensities of VI–VII on the Modified Mercalli scale at distances of 50–100 km. The combination of thrust and strike-slip faulting accommodates the oblique convergence between the Philippine Sea Plate and the Philippine archipelago. Ongoing GPS measurements confirm convergence rates of several centimeters per year, sustaining the potential for future large events. Continued monitoring by the Philippine Institute of Volcanology and Seismology and international networks remains essential for refining hazard assessments and supporting resilient infrastructure development in Mindanao.

References

USGS Earthquake Catalog (events 2001–2025) Philippine Institute of Volcanology and Seismology regional reports