Seismic Activity Near Nabire, Indonesia: The February 2004 Earthquake Sequence

Nabire lies in the Indonesian province of Papua on the western half of New Guinea, a region shaped by ongoing convergence between the Australian and Pacific plates. This tectonic setting produces frequent moderate-to-large earthquakes along thrust faults and strike-slip structures associated with the New Guinea fold-and-thrust belt and nearby subduction zones. The area experiences elevated seismicity because the leading edge of the Australian plate collides with and underthrusts the Pacific plate at rates of several centimeters per year. On 5 February 2004 at 21:05 UTC, a magnitude 7.0 earthquake struck 28 km south of Nabire at a focal depth of 16.6 km. The event occurred within a zone of active crustal deformation and was felt strongly across western Papua. Two days later, on 7 February, a magnitude 7.3 earthquake occurred 71 km from the first shock near the south coast of Papua. Later the same year, on 26 November, two magnitude 7.1 events took place near Nabire, one of them only 14 km from the February 5 epicenter. These four earthquakes form a notable cluster of M ≥ 7.0 activity within a 12-month period, highlighting the persistent seismic hazard in the Nabire region. Historical records show that western Papua has repeatedly experienced damaging earthquakes. The 2004 sequence fits a longer pattern of large thrust and strike-slip events driven by the same plate-boundary forces. Shallow focal depths, such as the 16.6 km depth recorded in February 2004, increase the potential for strong ground shaking in populated coastal and highland areas. Aftershock sequences following these mainshocks typically last weeks to months and can include additional events capable of causing further damage to infrastructure. Current seismic monitoring by regional and global networks continues to track microseismicity and afterslip in the Nabire area. Updated hazard assessments incorporate both the 2004 events and ongoing geodetic measurements that indicate steady strain accumulation along regional faults. Residents and authorities in Papua are advised to maintain earthquake-resistant building standards and preparedness plans given the demonstrated capacity of the region to generate multiple M7-class earthquakes within short time frames.

References

USGS Earthquake Catalog (events 2004-02-05, 2004-02-07, 2004-11-26)
Global CMT Catalog
Indonesian Meteorological, Climatological, and Geophysical Agency (BMKG) annual seismicity reports