Location:

Period:

23 Oct 2006 00:19:21 - 24 Oct 2006 04:45:37 (1 day 4 hours 26 minutes)

Volcanoes in 100km radius:

Balut(44km)

Earthquakes:

M 7.0+:

M 7.8; 26 km SW of Kablalan, Philippines; (7 Jun 2026) (74km from the swarm center)

7 swarms found nearby.

2002

PS20020306.1(123.8km)

5 Mar

22 hours

6 earthquakes

2009

PS20090211.1(185.1km)

11 Feb

2 days 11 hours

67 earthquakes

PS20090614.1(141.9km)

14 Jun

15 hours

5 earthquakes

2019

PS20191029.1(197.2km)

29 Oct

20 hours

10 earthquakes

PS20191215.1(178.1km)

15 Dec

6 hours

8 earthquakes

2026

PS20260608.1(20.6km)

7 Jun

3 days 12 hours

38 earthquakes

PS20260613.1(35.1km)

12 Jun

1 day 2 hours

6 earthquakes

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Seismic Swarm PS20061023.1: Analysis of the October 2006 Event Near Sarangani, Philippines

The seismic swarm designated PS20061023.1 occurred in a tectonically active region 48 km south-southwest of Sarangani, Philippines, within the southern portion of Mindanao. This area lies along the complex boundary where the Philippine Sea Plate subducts beneath the Eurasian Plate, contributing to frequent seismic activity characteristic of the Pacific Ring of Fire. The swarm initiated at 00:19 on 23 October 2006 and concluded at 04:45 on 24 October 2006, spanning 28 hours and 26 minutes during which 11 earthquakes were recorded.

Geological conditions in this part of the Philippines involve multiple fault systems, including segments of the Philippine Fault and associated thrust faults linked to subduction processes. Historical seismic records indicate that such swarms are uncommon in the immediate vicinity, with only one prior swarm documented since 1 January 2000, occurring in 2002. The 2006 event therefore represents a notable episode of clustered seismicity.

The sequence began with a magnitude 5.7 earthquake at a depth of 10 km at 00:19:21 on 23 October. Subsequent events included two magnitude 5.3 quakes within minutes of each other at 01:40:13 and 01:40:18, at depths of 10 km and 30 km respectively. Additional activity on the same day featured magnitudes ranging from 5.0 to 5.2 at depths between 10 km and 80 km. The swarm peaked on 24 October with a pair of magnitude 6.1 events at 03:03:45 and 03:03:51, recorded at depths of 10 km and 67 km. The sequence ended with a magnitude 5.1 event at 04:45:37 on 24 October at 10 km depth.

These events illustrate typical swarm behavior, with multiple moderate shocks occurring in rapid succession without a single dominant mainshock. Depths were predominantly shallow to intermediate, consistent with regional subduction-related seismicity. The swarm's timing and distribution provide insight into stress accumulation and release along local fault structures.

Since 1 January 2000, the region has also experienced a strong earthquake of magnitude 7.8 on 7 June 2026, located 26 km southwest of Kablalan and approximately 74 km from the swarm center. This underscores the ongoing seismic hazard in the Sarangani area driven by plate convergence.

Overall, the PS20061023.1 swarm highlights the dynamic geological setting of southern Mindanao, where subduction and fault interactions continue to generate clustered earthquake activity. Monitoring such episodes remains essential for understanding regional tectonics and assessing potential hazards.