Seismic Activity in Papua New Guinea: Focus on the 2015 Magnitude 7.5 Event

Papua New Guinea occupies a tectonically complex zone where the Pacific Plate converges with the Australian Plate and several smaller plates, including the Solomon Sea and South Bismarck plates. This interaction produces the New Britain subduction zone and associated transform faults, resulting in frequent moderate-to-large earthquakes at shallow to intermediate depths. The region around Kokopo and Kimbe on New Britain Island experiences elevated seismicity due to ongoing subduction and arc volcanism. On 5 May 2015 at 01:44 UTC, a magnitude 7.5 earthquake struck 131 km SSW of Kokopo at a depth of 55 km. The event occurred within the subducting slab, consistent with the region's intermediate-depth seismicity patterns. No stronger earthquakes have been recorded in the immediate vicinity since 2000. Notable events since 1 January 2000 include a magnitude 7.8 earthquake on 17 November 2000 located 138 km SSW of Kokopo (11 km from the 2015 epicenter), the 2015 magnitude 7.5 mainshock itself, and a magnitude 7.0 event on 10 October 2018 situated 119 km east of Kimbe (78 km from the 2015 location). These earthquakes reflect the persistent strain accumulation and release along the plate boundary. The geological setting features a narrow forearc, active volcanoes such as Rabaul Caldera near Kokopo, and rapid uplift of coastal terraces driven by both seismic and aseismic slip. Historical records document recurrent damaging events, underscoring the need for robust building codes and tsunami preparedness in this densely populated volcanic arc. References: USGS Earthquake Hazards Program catalog data for event parameters and regional tectonics summaries from Geoscience Australia and the Australian Plate Boundary project reports.