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Note:This page contains AI-generated content for informational and entertainment purposes only. It may contain inaccuracies. Raw event data is from USGS and EMSC. All statistics, lists, and derived information are generated by this site. Full disclaimerFound an error?
Location:
Mindanao, Philippines
Period:
14 Jun 2021 14:20:50 - 15 Jun 2021 20:07:37 (1 day 5 hours 46 minutes)
Volcanoes in 100km radius:
Kalatungan(28km), Musuan(34km), Ragang(34km), Makaturing(55km), Apo(92km)
Earthquakes:
27
No swarms nearby.
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20210615.1 in Mindanao, Philippines

A seismic swarm designated S20210615.1 occurred in Mindanao, Philippines, beginning at 14:20 on 14 June 2021 and concluding at 20:07 on 15 June 2021. Over this 29-hour, 46-minute period, 27 earthquakes were recorded. Magnitudes ranged from 3.0 to a peak of 5.7, with focal depths primarily between 1 km and 10 km. The sequence initiated with a magnitude 3.0 event at 14:20:50 on 14 June, followed shortly by the largest shock of magnitude 5.7 at 14:38:41 (5 km depth). Subsequent events included magnitudes of 5.3, 4.5, and multiple 3.5–4.3 shocks clustered through the afternoon and evening of 14 June. Activity continued overnight with smaller events (3.0–3.7) before tapering on 15 June, ending with a magnitude 3.1 event at 20:07:37.

Mindanao occupies a highly tectonically active segment of the Philippine Mobile Belt, where the Philippine Sea Plate converges with the Eurasian Plate. This interaction drives subduction along the Philippine Trench to the east and the Cotabato Trench to the west, while the left-lateral Philippine Fault transects the island. These structures produce frequent shallow crustal earthquakes and occasional swarms, often linked to fluid migration or stress transfer along fault segments rather than a single mainshock-aftershock sequence.

Historical records indicate that earthquake swarms are recurrent in the region. The prior swarm since 2000 occurred in 2019, underscoring the episodic nature of clustered seismicity in Mindanao. Depths in the 2021 swarm remained consistently shallow, consistent with activity along upper-crustal faults associated with the Philippine Fault System.

Such swarms highlight ongoing seismic hazard in Mindanao, where populations and infrastructure remain exposed to moderate-magnitude events capable of generating local ground shaking. Continued monitoring supports improved understanding of fault behavior in this convergent margin setting.

References
USGS Earthquake Catalog (earthquake.usgs.gov)
Philippine Institute of Volcanology and Seismology (PHIVOLCS) regional tectonics reports