Location:

Period:

23 Dec 2023 14:22:26 - 24 Dec 2023 05:56:02 (15 hours 33 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.6; 19 km E of Gamut, Philippines; (2 Dec 2023) (69km from the swarm center)

15 swarms found nearby.

2001

PS20010101.1(186.4km)

1 Jan

1 day 0 hours

9 earthquakes

2009

PS20090521.1(54.9km)

21 May

8 hours

5 earthquakes

2014

PS20140530.1(120.3km)

30 May

5 hours

6 earthquakes

PS20140531.1(120.2km)

31 May

1 hours

9 earthquakes

2018

PS20181029.1(60.3km)

29 Oct

7 hours

5 earthquakes

2019

PS20190208.1(176.4km)

8 Feb

9 hours

7 earthquakes

PS20190426.1(158.6km)

26 Apr

15 hours

9 earthquakes

2023

PS20231202.1(55.2km)

2 Dec

5 days 19 hours

107 earthquakes

S20231202.2(20.8km)

2 Dec

4 days 13 hours

158 earthquakes

S20231203.1(19.1km)

2 Dec

3 days 8 hours

49 earthquakes

S20231203.2(38.2km)

2 Dec

5 days 21 hours

67 earthquakes

S20231203.3(62.5km)

2 Dec

3 days 3 hours

41 earthquakes

PS20231212.1(30.8km)

11 Dec

14 hours

5 earthquakes

2024

PS20240803.1(38.2km)

2 Aug

5 hours

7 earthquakes

2025

PS20251010.1(121.4km)

10 Oct

1 day 8 hours

21 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm Activity in the Philippine Islands Region, December 2023

The Philippine Islands region lies within the tectonically complex Pacific Ring of Fire, where the Philippine Sea Plate converges with the Eurasian Plate. This interaction produces the Philippine Trench to the east and the Manila Trench to the west, along with the left-lateral Philippine Fault Zone that traverses the archipelago. These features generate frequent earthquakes, volcanic activity, and occasional seismic swarms as stress accumulates and releases across multiple fault systems.

SeismoSight recorded swarm PS20231224.1 from 14:22 on 23 December 2023 to 05:56 on 24 December 2023. Five earthquakes occurred within 15 hours and 33 minutes. Event parameters were as follows: a magnitude 5.1 shock at 41 km depth at 14:22:26 on 23 December; a magnitude 5.2 event at 35 km depth at 16:38:34 on 23 December; a magnitude 5.3 earthquake at 57 km depth at 02:20:44 on 24 December; a magnitude 5.1 shock at 51 km depth at 03:02:06 on 24 December; and a magnitude 3.1 event at 1 km depth at 05:56:02 on 24 December. The sequence clustered near the central Philippine Islands, an area known for intermediate-depth seismicity linked to subducting slabs.

Historical records maintained by SeismoSight indicate 13 swarms in the region since 1 January 2000. Earlier episodes occurred in 2001 (one swarm), 2009 (one), 2014 (two), 2018 (one), 2019 (two), and six in 2023. This recent increase aligns with ongoing tectonic loading along major faults. On 2 December 2023, a magnitude 7.6 earthquake struck 19 km east of Gamut, approximately 69 km from the swarm centroid, underscoring the proximity of significant seismic sources capable of influencing local stress fields.

Seismic swarms in this setting commonly reflect either fluid migration along faults or distributed strain release within the overriding plate. Depths ranging from shallow (1 km) to intermediate (57 km) suggest involvement of both crustal faults and the subducting slab interface. Such sequences rarely produce surface rupture but can elevate short-term seismic hazard through aftershock triggering or escalation into larger mainshocks.

Monitoring by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) complements global catalogs by providing rapid local assessments. Continued observation remains essential given the region’s history of destructive events and the potential for swarm activity to precede or accompany larger ruptures along the Philippine Fault.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
PHIVOLCS Seismic Bulletins (phivolcs.dost.gov.ph)
SeismoSight internal swarm classification PS20231224.1