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Manila Bulletin devider Philippines devider National devider 7.4, 6.8 Davao Oriental quakes considered 'doublet' — Phivolcs

7.4, 6.8 Davao Oriental quakes considered 'doublet' — Phivolcs

Published Oct 10, 2025 08:44 pm
PHIVOLCS
PHIVOLCS
The Philippine Institute of Volcanology and Seismology (Phivolcs) said the two strong earthquakes that struck Davao Oriental on Friday, Oct. 10, a magnitude 7.4 and a magnitude 6.8, may be considered a “doublet earthquake.”
“These are distinct earthquakes in almost the same area, with two (or more) main shocks that have slight differences in magnitude,” Phivolcs explained.
“This happens when faults or trenches cause stress that triggers a sequence of events,” it added.
Phivolcs Director Dr. Teresito Bacolcol clarified in a press conference on Friday evening that “this [6.8-magnitude quake] is a distinct event, not an aftershock.”
“This means these [7.4-magnitude and 6.8-magnitude earthquakes] are two separate events occurring,” he added.
Unlike a main shock–aftershock sequence, both quakes in a doublet are independent events but are believed to be triggered by the same fault or trench system releasing accumulated stress.
The agency added that said such events happen when faults or trenches cause stress to trigger a sequence of strong tremors.
The first earthquake, which struck at 9:43 a.m. on Friday, Oct. 10, had a magnitude of 7.4, with its epicenter located 44 kilometers northeast of Manay, Davao Oriental.
The second earthquake occurred at 7:12 p.m. the same day. It was initially reported as magnitude 6.9 but later updated to 6.8 after further analysis.
The 6.8-magnitude quake struck at a depth of 37 kilometers, with an epicenter located 43 kilometers southeast of Manay, Davao Oriental.
Bacolcol said this is not the first time a doublet earthquake has occurred along the Philippine Trench.
Past examples of doublet earthquakes include the 2023 Hinatuan earthquakes (magnitude 7.4 on Dec. 2 and magnitude 6.8 on Dec. 4) and the 1992 Manay earthquakes (magnitude 7.1 and 7.5), both associated with the Philippine Trench, which is the same undersea feature that influences seismic activity in eastern Mindanao.
The agency said it is continuing to analyze the earthquake parameters to further characterize the two events and understand their relationship.

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PHIVOLCS 7.4-MAGNITUDE 6.8-MAGNITUDE DOUBLET EARTHQUAKE
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