Phivolcs explains Davao Oriental quakes are a rare 'doublet'

The Philippine Institute of Volcanology and Seismology clarified that the two earthquakes that struck Davao Oriental on Friday are not connected. Phivolcs Director Teresito Bacolcol referred to the rare, similar-sized tremors as a "doublet."

“It’s a separate event. We have a term for that: it is a doublet. These are closely timed events, and they happen almost in the same area and they have almost the same magnitude,” he said.

According to Bacolcol, aftershocks are usually about one magnitude lower than the initial main shock. He also noted that doublets tend to occur along the same fault line.

“They usually occur when a fault or an earthquake generator is quite complicated, causing a trigger of a sequence of earthquake events. It is very common for the Philippines,” he said.

Bacolcol said that this wasn't the first time the Philippines has experienced a doublet, citing the earthquakes in 1972 and 2023.

Although the double earthquake sparked worries among citizens about a stronger tremor, Bacolcol reassured the public that the probability of this happening is "very small."

"Kasi kung magti-trigger pa siya ng mas malaking event–magnitude-7.5 or 7.6–yung mga nangyayaring events natin that would become foreshock, then we’ll have the main shock,” he said. 

“The determination ng foreshock is always in the hindsight,” he said.

At around 10 a.m. on Friday, a magnitude 7.4, hit about 20 kilometers off Manay town in the Mindanao region.

Another earthquake with a magnitude of 6.7 rocked the same area almost 10 hours later.

According to reports, at least eight people died.