Powerful quake that jolted Mindanao, Visayas explained

Local

FEAR rippled across the south on Friday morning after a magnitude 7.4 earthquake rocked Davao Oriental, shaking large parts of Mindanao and Visayas.

However, experts assured the public it was not connected to the recent magnitude 6.9 quake that hit Cebu.

A powerful offshore earthquake struck at 9:43 a.m. on October 10, with its epicenter located 62 kilometers east of Manay town in Davao Oriental, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

The quake, initially measured at magnitude 7.6, was later downgraded to 7.4 after further analysis.

The tremor, which had a shallow depth of only 10 kilometers, sent people rushing outdoors as strong shaking was felt across Davao, Surigao, and parts of the Visayas, including Cebu City.

Phivolcs reported Intensity V in Davao City and Intensity IV in Bislig, Surigao del Sur.

Instrumental readings also showed widespread shaking: Intensity V in several areas, including Gingoog City, Misamis Oriental; Davao de Oro; and Kidapawan, Cotabato; and Intensity IV in Cebu City, Cagayan de Oro, Tacloban, and General Santos.

Phivolcs warned of possible damage and aftershocks, while issuing a tsunami warning for coastal areas along the eastern seaboard of Mindanao and Eastern Visayas.

Residents of Eastern Samar, Leyte, Southern Leyte, Dinagat Islands, Surigao del Norte, Surigao del Sur, and Davao Oriental were advised to immediately move to higher ground.

Phivolcs Director Dr. Teresito Bacolcol confirmed in a press briefing that the quake originated from the Philippine Trench, one of the country’s most active subduction zones.

“We have six active trenches in the country. The earthquake that happened this morning came from the Philippine Trench, which is one of our most active seismic generators,” Bacolcol said.

He noted that the 9:43 a.m. tremor occurred at a depth of 23 kilometers, consistent with the depth range of quakes generated by active subduction zones.

The agency also recorded 179 aftershocks by 1 p.m., some of which were felt in nearby provinces. Bacolcol advised the public to remain vigilant for possible smaller tremors in the coming days.

The Pacific Tsunami Warning Center in Hawaii also issued a tsunami alert shortly after the quake, but later lifted it after no significant sea-level rise was observed.

Phivolcs confirmed a minor sea-level increase of about 30 centimeters in Tandag, Surigao del Sur, but clarified that no destructive waves occurred.

“We have an SOP to lift the tsunami warning two hours after the estimated arrival time. By 1:43 p.m., we can declare the area safe if no significant sea-level rise is observed,” Bacolcol said.

Phivolcs also dispelled fears that the Davao tremor was connected to the magnitude 6.9 earthquake that struck Bogo City, Cebu, on September 30.

“These earthquakes are independent events,” Bacolcol clarified. “The Davao quake came from the Philippine Trench, while the Cebu earthquake was generated by a local fault system within the Visayas. They are too far apart to be connected.”

He explained that the Philippines experiences about 30 earthquakes daily due to its complex network of active faults and trenches.

“These are not all connected unless the faults are very close to each other. In this case, Cebu and Mindanao are too distant,” he added.

Bacolcol said strong earthquakes have repeatedly occurred in the same region along the Philippine Trench.

“In 1921, a magnitude 7.5 quake occurred; in 1929, 7.2; in 1952, 7.6; and in 1924, 8.3—all along this trench,” he said.

The Philippine Trench, which runs parallel to the country’s eastern seaboard, forms part of the Pacific Ring of Fire, a vast zone known for frequent earthquakes and volcanic activity.

The Phivolcs chief urged the public to remain calm yet prepared. It noted that the country’s position on the Pacific Ring of Fire makes earthquakes a natural part of life in the Philippines.

“I understand that many of our kababayans are experiencing disaster fatigue,” Bacolcol said. “But we have to accept the reality that we live in an active seismic region. Instead of being afraid, we must always be prepared.”(TGP)