The 2004 M7.3 Earthquake Near the South Coast of Papua, Indonesia

The M7.3 earthquake that struck near the south coast of Papua, Indonesia, on 7 February 2004 at 02:42 local time originated at a shallow depth of 10 km. This event formed part of an intense seismic sequence in early 2004 within a tectonically active region known for frequent moderate-to-large earthquakes. Papua lies at the complex convergent boundary between the Australian and Pacific plates. The interaction produces a combination of subduction, thrust faulting, and strike-slip motion along structures such as the New Guinea Trench and the Sorong Fault system. These features accommodate rapid convergence rates exceeding 10 cm per year in places, resulting in high seismic hazard across western New Guinea. Shallow crustal earthquakes are common because many active faults extend to the surface in this fold-and-thrust belt setting. Three notable events illustrate the 2004 sequence. The M7.3 mainshock was followed closely in time by an M7.0 earthquake on 5 February located 28 km south of Nabire and an M7.1 event on 26 November situated 29 km south-southwest of Nabire. The M7.3 occurred essentially at the same location as the reference point used for distance calculations, while the other two events lay 60–71 km away. All three shocks were relatively shallow and capable of generating strong ground shaking in nearby coastal and highland communities. The broader seismic history of the region shows repeated clusters of large earthquakes. Papua and western New Guinea have recorded multiple magnitude-7+ events throughout the instrumental era, reflecting the ongoing plate-boundary deformation. Such sequences often involve both the main plate interface and subsidiary faults within the overriding plate, producing aftershock distributions that can extend for weeks to months. Ground shaking from the February 2004 mainshock was felt widely across southern Papua, with potential for localized landslides in steep terrain and minor coastal effects. No widespread tsunami was generated, consistent with the event’s moderate magnitude and lack of significant vertical seafloor displacement. Ongoing monitoring by regional and global seismic networks continues to refine understanding of fault segmentation and recurrence intervals in this rapidly deforming area. The 2004 sequence underscores the persistent seismic risk associated with Papua’s position at an active plate margin.

References

USGS Earthquake Catalog (events 2004) Global CMT Project focal mechanisms Tectonic framework summaries from the Australian Plate–Pacific Plate boundary studies