Seismic Swarm PS20041126.1: Analysis of the November 2004 Event Near Nabire, Indonesia

Seismic swarm PS20041126.1 was recorded in the region 27 km west-southwest of Nabire, Indonesia. The sequence began at 18:52 on 25 November 2004 and concluded at 09:48 on 27 November 2004, spanning 38 hours and 56 minutes during which 12 earthquakes were registered.

The temporal progression opened with a magnitude 5.3 event at a depth of 11 km. Within hours, two magnitude 7.1 earthquakes occurred at 02:25 on 26 November, one at 10 km depth and the second at 33 km depth. Subsequent events included a magnitude 5.2 at 10 km, followed by several magnitude 5.0–5.9 shocks clustered at depths between 10 km and 60 km. The sequence closed with a magnitude 5.8 event at 10 km depth on 27 November.

This swarm occurred in a region of Papua, Indonesia, characterized by ongoing tectonic interactions along the boundary between the Australian and Pacific plates. The area has experienced repeated seismic activity, consistent with the historical record of two swarms since 1 January 2000, the first of which is the 2004 sequence documented here.

Strong earthquakes in the vicinity since 2000 include the magnitude 7.1 event of 26 November 2004 located 65 km from the swarm center, a second magnitude 7.1 shock on the same date only 5 km from the center, a magnitude 7.3 earthquake on 7 February 2004 at 66 km distance, and a magnitude 7.0 event on 5 February 2004 positioned 12 km from the swarm center. These events underscore the persistent seismic hazard in the Nabire district.

The 2004 swarm illustrates typical characteristics of clustered seismicity in subduction-influenced zones, where multiple moderate-to-large events occur over short intervals without a single dominant mainshock. Depths ranging from 10 km to 60 km align with the structural complexity of the regional crust and upper mantle.

• SeismoSight internal swarm classification records
• Historical earthquake catalog since 1 January 2000