PHIVOLCS detects 3,000 tremors in Mindanao before Magnitude 7.8 earthquake

Over 3,000 weak and successive earthquakes have been monitored in southern Mindanao from 2025 until January of this year, months before the magnitude 7.8 earthquake struck the island on Monday, according to scientists from the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

According to Raffy Tima’s report on “24 Oras,” PHIVOLCS scientists released the study on May 15 regarding the Cotabato Trench.

“Very timely ‘yung paglabas namin ng study. Kasi we are talking about the same trench eh,” said PHIVOLCS science research specialist Deo Carlo Llamas.

(The release of our study was very timely because we are talking about the same trench.)

“Sana ‘yung study namin naipakita namin sa publiko na ‘yung Cotabato Trench even though na ang last na magnitude, malakas na magnitude na prinoduce nito ay noon 1976 ay still active,” he added.

(We hope our study has shown the public that the Cotabato Trench is still active, even though the last strong-magnitude earthquake it generated was in 1976.)

The PHIVOLCS scientist is referring to the Magnitude 8.1 Moro Gulf quake in 1976, which is considered the most destructive earthquake in Philippine history.

The deadly earthquake occurred at 12:11 a.m. on August 17, 1976, while most of the people were sleeping.

But Llamas clarified that the section of the Cotabato Trench that moved on Monday was different from the area where they observed the earthquake swarm in their study.

“‘Yung nangyaring swarm nasa northern segment ng Cotabato Trench at ‘yung nangyaring magnitude 7.8 recently ay mas southern part pa no, nasa third part ng Cotabato Trench,” he said.

(The earthquake swarm occurred in the northern segment of the Cotabato Trench, while the recent magnitude 7.8 earthquake occurred farther south, in the third segment of the Cotabato Trench.)

“Pero based sa study namin, ‘yung pinapakita lang kasi namin sa study namin na aktibo ang Cotabato Trench.”

(But based on our study, what we are showing is simply that the Cotabato Trench is active.)

While an earthquake swarm cannot necessarily be considered an indication of an impending major earthquake, it should still serve as a warning that the area is seismically active, authorities said. Residents in the area should remain prepared at all times. –Vince Angelo Ferreras/NB, GMA News