Location:

Period:

22 Oct 2007 06:11:12 - 22 Oct 2007 12:14:41 (6 hours 3 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

6 swarms found nearby.

2001

PS20011007.1(183.6km)

7 Oct

5 hours

5 earthquakes

2007

PS20070722.1(38.5km)

22 Jul

4 hours

6 earthquakes

PS20070806.1(19.4km)

5 Aug

15 hours

6 earthquakes

2016

PS20160917.1(124.0km)

17 Sep

1 day 5 hours

6 earthquakes

2023

S20230103.1(87.9km)

2 Jan

3 days 0 hours

47 earthquakes

S20230209.2(95.9km)

8 Feb

3 days 8 hours

50 earthquakes

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Seismic Swarm Analysis: Vanimo Region, Papua New Guinea, October 2007

On 22 October 2007, a seismic swarm designated PS20071022.1 was recorded 24 km southeast of Vanimo in Papua New Guinea’s Sandaun Province. The sequence began at 06:11 UTC and concluded at 12:14 UTC, encompassing five earthquakes within a six-hour window. Magnitudes ranged from 4.9 to 5.4, with focal depths between 32 km and 54 km.

The events unfolded rapidly. The initial shock measured 5.4 at 49 km depth, followed minutes later by a 5.0 event at 35 km. Two additional events near 5.0–5.1 occurred around 08:17–08:18 at depths of 44 km and 54 km. The final recorded earthquake reached 4.9 at 32 km depth. All activity remained tightly clustered in both space and time, characteristic of swarm behavior rather than a classic mainshock-aftershock sequence.

Papua New Guinea occupies one of the world’s most tectonically active zones at the collision boundary between the Australian and Pacific plates. The northern margin features oblique convergence accommodated along the New Guinea Trench and associated strike-slip structures. Vanimo lies near the eastern termination of this trench system, where the plate boundary transitions into the Bewani-Torricelli fault zone and the broader Papua New Guinea orogenic belt. Historical seismicity in the region reflects both shallow crustal faulting and intermediate-depth events linked to subducting slabs.

Since 2000, only three swarms have been identified in the catalog for this sector of Papua New Guinea. A single swarm occurred in 2001, while two swarms, including the 2007 sequence, took place that year. Such low recurrence underscores that swarm activity remains infrequent compared with the steady background rate of isolated earthquakes driven by regional convergence.

These short-lived clusters provide insight into transient stress perturbations along mature fault networks. The 2007 swarm’s narrow depth range and rapid onset suggest localized fluid migration or aseismic slip may have triggered the sequence, consistent with patterns observed in other convergent-margin settings. Continued monitoring of similar episodes remains essential for refining seismic hazard assessments in this densely populated coastal corridor.

References

USGS Earthquake Catalog (ANSS Comprehensive Catalog)
Global CMT Project
Papua New Guinea Geological Survey regional tectonic summaries