What is it? Twin Davao Oriental earthquakes a doublet, says PHIVOLCS

A magnitude 7.4 earthquake struck 43 kilometers east of Manay, Davao Oriental, at 9:43 a.m. on Friday.

Hours later, a separate event, this time a magnitude 6.8 earthquake, hit 36 kilometers south of Manay at 7:12 p.m. PHIVOLCS said the second earthquake was not an aftershock but the latter half of a doublet.

PHIVOLCS director Teresito Bacolcol said a “doublet” refers to two closely-timed earthquakes happening nearby. 

“A doublet earthquake means two closely timed quakes happening nearby. They happen in the same area but have different epicenters and strengths,” Bacolcol told GMA News Online. 

“Aftershocks are usually one magnitude lower than the main shock,” he added.

As of 9 p.m., PHIVOLCS recorded 498 aftershocks from both earthquake events. 

According to PHIVOLCS, aftershocks are “small earthquakes that follow a larger earthquake (mainshock). The aftershocks may continue to occur for several days and weeks, some of which may be felt.” 

PHIVOLCS said that this is not the first time that a doublet earthquake has occurred. Bacolcol said that a similar situation happened in 1992 and 2023. 

“This is not the first time na nangyari po ito along the Philippine Trench. On May 17, 1992, we had magnitude 7.1 and magnitude 7.5, separated only by around 26 minutes. And these two events were only 20 kilometers from each other,” the PHIVOLCS director said in a press briefing. 

“The most recent would be the Hinatuan earthquake in 2023. We have a magnitude 7.4 on Dec. 2 and two days after another event happened, on Dec. 4, with a magnitude of 6.8. Again, ang term natin dito ay doublet, they are distinct earthquakes.” 

PHIVOLCS also clarified that the Davao Oriental quakes are not related to the magnitude 6.9 earthquake that jolted Bogo City, Cebu, last September 30. 

“Wala pong koneksyon po ‘yan. Yung nag-generate ng lindol sa Cebu, yung magnitude 6.9, last September 30 is the Bogo Bay Fault. Ito naman is the Philippine Trench. Magkalayo sila, wala silang connection,” Bacolcol said. 

(They are not connected. What triggered the earthquake in Cebu, the magnitude 6.9 last September 30 is the Bogo Bay Fault. This one is the Philippine Trench. They are far apart, they have no connection.) –NB, GMA Integrated News