Location:

Period:

2 Mar 2018 00:57:11 - 2 Mar 2018 21:30:55 (20 hours 33 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.5; 32 km SW of Tari, Papua New Guinea; (25 Feb 2018) (7km from the swarm center)

5 swarms found nearby.

2012

PS20121208.1(189.4km)

8 Dec

14 hours

5 earthquakes

2018

PS20180225.2(19.0km)

25 Feb

2 days 11 hours

40 earthquakes

PS20180225.1(107.0km)

25 Feb

1 hours

8 earthquakes

PS20180304.1(26.8km)

4 Mar

8 hours

5 earthquakes

PS20180306.1(29.5km)

6 Mar

1 day 15 hours

13 earthquakes

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Seismic Swarm Analysis: PS20180302.1 Near Tari, Papua New Guinea

On 2 March 2018, a seismic swarm designated PS20180302.1 was recorded approximately 30 km south-southwest of Tari in Papua New Guinea’s Southern Highlands Province. The sequence began at 00:57 UTC and concluded at 21:30 UTC, encompassing six earthquakes over a span of 20 hours and 33 minutes. Magnitudes ranged from 4.4 to 5.3, with focal depths predominantly at 10 km except for one event at 7 km. The individual events occurred at 00:57 (M5.1), 03:01 (M5.3), 03:14 (M5.1), 07:17 (M4.4), 07:59 (M5.1), and 21:30 (M5.2).

This swarm unfolded in a tectonically complex region where the Australian Plate converges with the Pacific Plate along the New Guinea Trench and associated strike-slip systems. The area experiences frequent shallow crustal seismicity due to oblique subduction and regional fault networks. Papua New Guinea ranks among the world’s most earthquake-prone nations, with historical records documenting repeated moderate-to-large events in the highlands.

Notably, the swarm followed a magnitude 7.5 earthquake on 25 February 2018 located 32 km southwest of Tari, only 7 km from the swarm centroid. Such aftershock sequences and triggered swarms are common in the aftermath of major ruptures along active thrust and strike-slip faults in the region. Historical data indicate that only three swarms have been identified in the vicinity since 2000, occurring in 2012 (one swarm) and 2018 (two swarms), underscoring the episodic nature of clustered seismicity here.

Geological mapping of the Tari area reveals Quaternary sediments overlying folded and faulted Mesozoic to Cenozoic bedrock, with active structures capable of producing both mainshock-aftershock sequences and swarm-type activity. Depths around 7–10 km align with typical shallow crustal faulting observed across the highlands.

Continued monitoring remains essential given the proximity of population centers to these active structures. The 2018 events illustrate how moderate swarms can punctuate periods of elevated seismic hazard following larger regional earthquakes.

References:
USGS Earthquake Catalog (earthquake.usgs.gov)
Global CMT Catalog (globalcmt.org)
Geological Survey of Papua New Guinea regional reports