Southern Mindanao was rattled on the evening of Friday, June 26, when a magnitude 6.6 earthquake struck offshore waters southwest of Davao Occidental, prompting reports of strong shaking from communities spanning several provinces. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) confirmed the event and issued its initial bulletin shortly after the tremor was felt.
Quake Details and Location
According to PHIVOLCS, the earthquake occurred at 7:34 in the evening and was centered approximately 90 kilometers south, 12 degrees west of Balut Island, which belongs to the island municipality of Sarangani in Davao Occidental. The coordinates were placed at 4.62 degrees north latitude and 125.24 degrees east longitude. The agency recorded a shallow focal depth of just 10 kilometers, classifying the event as tectonic in origin.
Shallow earthquakes of this depth tend to produce more intense ground shaking at the surface compared to deeper seismic events, which may explain the wide geographic spread of reported tremors across southern Mindanao provinces.
Shaking Intensity Across Affected Areas
PHIVOLCS recorded Intensity V — the highest reported shaking level from this event — in Kiamba in the province of Sarangani. This level of shaking is generally described as strong enough to awaken sleeping individuals and cause hanging objects to swing noticeably.
Intensity IV shaking was reported in Don Marcelino and Santa Maria, both located in Davao Occidental. In Davao City and Matanao in Davao del Sur, residents felt Intensity III tremors. The City of Digos in Davao del Sur, along with Monkayo, Mawab, and Maragusan in Davao de Oro, registered Intensity II shaking.
Instrumental Readings Spread Across Mindanao
Beyond the directly reported intensities, PHIVOLCS also released instrumental intensity readings gathered from its network of seismographs across the region. The agency's instruments logged the highest instrumental intensity — Level V — in Malapatan, Sarangani, and in T'boli, South Cotabato.
Instrumental Intensity IV was captured in several municipalities within Sarangani, specifically Malungon, Maitum, Kiamba, and Maasim, as well as in Tupi and the City of Koronadal in South Cotabato.
Instrumental Intensity III readings were recorded in Santa Maria in Davao Occidental, Tampakan in South Cotabato, and Palimbang in Sultan Kudarat. Lower-level readings of Intensity II and I extended further, reaching Magsaysay in Davao del Sur; the municipalities of Norala, Banga, Santo Niño, and Surallah in South Cotabato; Lebak, Isulan, Kalamansig, and President Quirino in Sultan Kudarat; Magpet, M'lang, and President Roxas in Cotabato; and Columbio and Esperanza, also in Sultan Kudarat.
Aftershocks Expected; Residents Urged to Stay Vigilant
PHIVOLCS reminded residents in all affected areas to remain on alert in the hours and days following the main tremor, as aftershocks are considered likely after an event of this magnitude. The agency advised the public to carefully inspect their homes, offices, and other structures for visible cracks, structural damage, or any signs of instability before re-entering or continuing to occupy buildings.
Residents are also encouraged to follow official advisories and avoid spreading unverified information that could cause unnecessary panic in affected communities.
Monitoring Continues
PHIVOLCS released the initial report as Earthquake Information No. 1, noting that the agency would continue monitoring the situation and may publish revised or updated data as additional information becomes available from its monitoring network. The public is advised to refer only to official PHIVOLCS bulletins for the latest and most accurate seismic information.
No tsunami warning was mentioned in the initial bulletin issued by PHIVOLCS regarding the June 26 earthquake off Davao Occidental.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)