Location:

Period:

29 Oct 2019 01:04:43 - 29 Oct 2019 21:22:07 (20 hours 17 minutes)

Volcanoes in 100km radius:

Apo(30km), Matutum(44km), Melebingoy(76km)

Earthquakes:

9 swarms found nearby.

2001

PS20010101.1(189.3km)

1 Jan

1 day 0 hours

9 earthquakes

2002

PS20020306.1(117.5km)

5 Mar

22 hours

6 earthquakes

2006

PS20061023.1(197.2km)

23 Oct

1 day 4 hours

11 earthquakes

2010

PS20100723.1(170.0km)

23 Jul

13 hours

11 earthquakes

2019

PS20191215.1(22.2km)

15 Dec

6 hours

8 earthquakes

S20191215.1(23.1km)

15 Dec

4 days 21 hours

56 earthquakes

2021

S20210615.1(109.0km)

14 Jun

1 day 5 hours

27 earthquakes

2026

PS20260127.1(152.2km)

27 Jan

1 day 7 hours

15 earthquakes

PS20260613.1(167.7km)

12 Jun

1 day 2 hours

6 earthquakes

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Seismic Swarm PS20191029.1 Near Telafas, Philippines: Event Analysis and Regional Context

A seismic swarm designated PS20191029.1 occurred on 29 October 2019, approximately 6 km east-northeast of Telafas in the Philippines. The sequence began at 01:04 and concluded at 21:22 local time, encompassing 10 earthquakes over a span of 20 hours and 17 minutes. All events were recorded at shallow depths between 10 and 15 km, with magnitudes ranging from 4.8 to 6.6.

The earthquakes unfolded as follows: an initial M6.6 event at 01:04:43 (15 km depth), followed by an M5.6 at 01:09:01 (14 km), M5.3 at 01:13:35 (10 km), M5.1 at 01:28:03 (10 km), M4.8 at 02:20:29 (10 km), M5.0 at 02:22:34 (10 km), M5.9 at 02:42:38 (10 km), M5.4 at 08:33:12 (10 km), M5.2 at 08:46:02 (10 km), and a final M5.0 at 21:22:07 (12 km). The swarm exhibited a rapid onset with the largest event occurring first, succeeded by smaller after-events clustered at similar depths.

Such swarms represent clusters of seismicity without a dominant mainshock, often linked to fluid migration or stress adjustments along fault systems. In this instance, the tight temporal and spatial grouping, combined with consistent shallow focal depths, aligns with typical swarm characteristics observed in tectonically active margins.

The Philippines lies within the Pacific Ring of Fire, where complex interactions among the Philippine Sea Plate, Eurasian Plate, and smaller crustal blocks drive frequent seismic activity. Subduction along the Philippine Trench and the presence of the Philippine Fault System contribute to elevated seismicity in the southern regions, including areas near Telafas. Historical records indicate moderate to large earthquakes recur due to strike-slip and thrust faulting in Mindanao and adjacent islands.

Since 2000, four prior swarms have been documented in the vicinity: one each in 2001, 2002, 2006, and 2010. These episodes underscore the recurrent nature of clustered seismicity in the region, potentially associated with ongoing tectonic strain accumulation.

Continued monitoring by national agencies remains essential for assessing evolving hazard levels in this high-seismicity zone.

References

Philippine Institute of Volcanology and Seismology (PHIVOLCS) seismic bulletins
United States Geological Survey (USGS) Earthquake Catalog
SeismoSight internal swarm classification records