Seismic Activity in Papua New Guinea: The 2019 Bulolo Earthquake

Papua New Guinea sits at the complex boundary between the Australian and Pacific tectonic plates, making it one of the most seismically active regions on Earth. The country experiences frequent earthquakes due to subduction, collision, and strike-slip faulting along its northern margin. This tectonic setting has produced a long history of strong events, with many occurring at intermediate depths within the subducting slab. On 6 May 2019 at 21:19 local time, a magnitude 7.1 earthquake struck 32 km northwest of Bulolo in Morobe Province. The event occurred at a depth of 146 km, placing it well within the mantle portion of the subducting plate. Deep-focus earthquakes of this type are common in the region and often produce less surface damage than shallower events of similar magnitude because much of the energy dissipates before reaching the ground. The 2019 Bulolo earthquake fits within a pattern of strong seismicity recorded since 2000. Notable events in the broader area include a magnitude 7.6 earthquake on 10 September 2022 located 70 km east of Kainantu, approximately 75 km from the 2019 epicenter. Another magnitude 7.1 event occurred on 14 December 2011, 25 km south-southeast of Wau and roughly 75 km from the 2019 location. These three events illustrate the repeated release of strain along the same segment of the plate boundary. Geological studies show that the crust beneath eastern Papua New Guinea consists of accreted island-arc terranes and ophiolite complexes formed during the Cenozoic. The ongoing convergence between the Australian plate and the Bismarck Sea plate drives both shallow crustal deformation and deeper Wadati-Benioff zone seismicity. Historical records document destructive earthquakes in 1906, 1910, and 1953, confirming that large-magnitude events have repeatedly affected the highlands and coastal lowlands. Although the 2019 earthquake was widely felt across Morobe Province and parts of the Highlands, its depth limited strong ground shaking at the surface. Aftershock sequences were modest compared with shallow crustal events. The region continues to be monitored by the Papua New Guinea Geological Survey and international seismic networks to improve understanding of fault behavior and to support hazard mitigation.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Geological Survey of Papua New Guinea annual reports