The 2018 M7.5 Earthquake Near Tari, Papua New Guinea

On 25 February 2018 at 17:44 local time, a magnitude 7.5 earthquake struck 32 km southwest of Tari in Papua New Guinea’s Southern Highlands Province. The event occurred at a focal depth of 25.2 km. This earthquake stands as one of the strongest recorded in the country since 2000 and released significant seismic energy across a tectonically active region. Papua New Guinea occupies a complex tectonic environment at the convergent boundary between the Australian and Pacific plates. The island of New Guinea experiences ongoing oblique collision and subduction, with the Australian plate moving northward relative to the Pacific plate at rates of approximately 70–100 mm per year. This interaction produces a network of thrust faults, strike-slip structures, and microplates that accommodate strain. The Southern Highlands lie near the Papuan Fold and Thrust Belt, where sedimentary rocks are deformed by compressional tectonics. Frequent moderate-to-large earthquakes reflect this persistent plate-boundary activity. Historical records document numerous destructive events in Papua New Guinea. Notable examples include the 1998 magnitude 7.0 earthquake near Aitape, which triggered a tsunami, and earlier 20th-century shocks that caused widespread landslides in highland terrain. Seismicity since 2000 has remained elevated, with the 2018 Tari event representing the largest in the instrumental catalog for the immediate area. The region’s steep topography and high rainfall amplify secondary hazards such as landslides and river damming following strong shaking. The 2018 mainshock was followed by an energetic aftershock sequence that continued for weeks. Ground shaking reached intensity VII–VIII in parts of the highlands, damaging infrastructure and triggering thousands of landslides. The combination of thrust faulting and the area’s rugged geology contributed to the observed surface effects. Post-event studies confirmed that rupture occurred on a northeast-dipping reverse fault within the fold-and-thrust belt. Ongoing monitoring by regional seismic networks continues to refine understanding of fault segmentation and strain accumulation. Improved building codes and landslide early-warning initiatives have been implemented in response to lessons from the 2018 sequence. As the plate-boundary processes remain active, future large earthquakes are expected in the highlands and surrounding regions.

References

USGS Earthquake Catalog (event page for 2018-02-25 M7.5 Papua New Guinea)
Global CMT Catalog
Geological Survey of Papua New Guinea seismic reports