Location:

Period:

6 Mar 2018 02:52:30 - 7 Mar 2018 18:11:07 (1 day 15 hours 18 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.5; 32 km SW of Tari, Papua New Guinea; (25 Feb 2018) (35km from the swarm center)

5 swarms found nearby.

2012

PS20121208.1(167.2km)

8 Dec

14 hours

5 earthquakes

2018

PS20180225.2(37.1km)

25 Feb

2 days 11 hours

40 earthquakes

PS20180225.1(93.0km)

25 Feb

1 hours

8 earthquakes

PS20180302.1(29.5km)

2 Mar

20 hours

6 earthquakes

PS20180304.1(11.7km)

4 Mar

8 hours

5 earthquakes

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Seismic Swarm PS20180306.1 Near Tari, Papua New Guinea

Seismic swarm PS20180306.1 was recorded 123 km south of Tari in Papua New Guinea, commencing at 02:52 on 6 March 2018 and concluding at 18:11 on 7 March 2018. Over 39 hours and 18 minutes, the sequence comprised 13 earthquakes with magnitudes ranging from 5.0 to 6.7, all at shallow depths between 10 km and 20 km.

The largest event reached magnitude 6.7 at 14:13 on 6 March 2018. Subsequent shocks maintained magnitudes between 5.0 and 5.5, with most occurring at 10 km depth. This pattern indicates a concentrated release of strain along a localized fault segment following the major magnitude 7.5 earthquake of 25 February 2018, located 32 km southwest of Tari and approximately 35 km from the swarm epicenter.

Papua New Guinea lies within the tectonically complex boundary between the Australian and Pacific plates. Convergence along the New Guinea Trench and associated strike-slip faults produces frequent moderate to large earthquakes. The region around Tari forms part of the Papuan Fold and Thrust Belt, where compressional tectonics have shaped the highlands over millions of years. Historical records show elevated seismicity, with the February 2018 magnitude 7.5 event exemplifying the potential for significant ground shaking in this setting.

Since 1 January 2000, five seismic swarms have occurred in the area. One swarm took place in 2012, while four were documented in 2018, underscoring episodic clustering of activity. Such swarms typically reflect aftershock sequences or fluid migration along faults rather than independent mainshock-aftershock progressions.

The March 2018 swarm illustrates how a preceding large earthquake can trigger secondary sequences days to weeks later. Depths remained consistently shallow, consistent with the regional crustal structure where brittle failure occurs above approximately 20 km. No surface rupture was reported, aligning with the moderate magnitudes involved.

This event contributes to understanding seismic hazard in the highlands, where population centers face risks from both direct shaking and secondary effects such as landslides. Continued monitoring supports improved models of strain accumulation along the plate boundary.

References
USGS Earthquake Catalog (historical events and locations)
Global CMT Project (focal mechanisms and depths)
SeismoSight internal swarm classification PS20180306.1