Seismic Hazards in the Kokopo Region, Papua New Guinea

The Kokopo area of East New Britain lies within one of the most tectonically active segments of the Pacific Ring of Fire. Here the Pacific Plate subducts beneath the Bismarck Sea and Solomon Sea plates along the New Britain Trench, generating frequent intermediate-depth earthquakes. The regional geology is dominated by the northward subduction of the Solomon Sea Plate at rates exceeding 10 cm per year, producing a well-defined Wadati-Benioff zone that extends to depths greater than 200 km. Volcanic arcs, including the active Rabaul caldera immediately north of Kokopo, form directly above this subduction zone. On 17 December 2016 at 10:51 UTC a magnitude 7.9 earthquake occurred 140 km east of Kokopo at a focal depth of 94.5 km. This event remains the largest in the immediate vicinity since 2000. Earlier strong earthquakes recorded in the same source region include a magnitude 7.6 event on 9 September 2005 located 135 km east of Kokopo, a magnitude 7.8 shock on 16 November 2000 situated 135 km southeast of Kokopo, a magnitude 7.3 earthquake on 7 July 2013 centered 190 km east-northeast of Kokopo, and a magnitude 7.0 event on 29 October 2000 located 191 km east-southeast of Kokopo. All five events occurred within a compact 100 km radius, underscoring persistent seismic strain accumulation along the subduction interface. These earthquakes exhibit thrust-faulting mechanisms consistent with plate convergence. Depths between 80 km and 150 km place the hypocenters within the subducting slab rather than at the shallow megathrust, reducing tsunami potential while still producing strong ground shaking felt across New Britain and New Ireland. Historical records document similar intermediate-depth events in the early twentieth century, indicating that the present pattern is long-standing rather than anomalous. Ongoing monitoring by regional seismic networks shows continued aftershock activity and background seismicity, reinforcing the need for earthquake-resistant construction standards in Kokopo and surrounding communities. The combination of rapid plate motion, a steeply dipping slab, and proximity to population centers keeps the region among the highest seismic hazard zones in the southwest Pacific.

References

USGS Earthquake Catalog (event parameters for 2000–2016). Global CMT Project (focal mechanisms for listed events).