THE series of earthquakes that recently shook parts of the Philippines — including major tremors in Davao Oriental, Zambales and Southern Leyte — are not part of a single massive event but a normal display of the country’s highly active geological nature.
The earthquakes occurred in succession after the magnitude 6.9 quake that struck northern Cebu on Sept. 30, 2025, which has since recorded more than 10,000 aftershocks.
Contrary to speculation that these events are connected, Philippine Institute of Volcanology and Seismology (Phivolcs) Director Teresito Bacolcol told SunStar Cebu on Sunday, Oct. 12, 2025, that the earthquakes in early October were independent occurrences with different geological origins.
Why so many earthquakes
The recent spate of tremors is a direct consequence of the Philippines’ location within the Pacific Ring of Fire — a horseshoe-shaped zone around the Pacific Ocean known for frequent earthquakes and volcanic eruptions caused by intense tectonic activity.
The country lies at the intersection of several massive sections of the Earth’s crust, known as tectonic plates, that constantly collide and grind against each other. The stress from these interactions is released as earthquakes.
Bacolcol said such activity is expected. “We have around 180 active fault segments and six active trenches. It’s possible for these to move in succession or simultaneously,” he said.
Different geological sources
Although the quakes occurred close in time, they came from separate underground generators:
Zambales quake: Triggered by movement along the Manila Trench, which runs along the western side of Luzon.
Southern Leyte and Surigao del Sur quakes: Caused by movements along different segments of the Philippine Trench off the country’s eastern coast.
The Davao Oriental doublet
A magnitude 7.4 and a magnitude 6.8 quake struck near Manay, Davao Oriental, on Oct. 10. Phivolcs classified them as an “earthquake doublet.”
Bacolcol explained that a doublet occurs when two large earthquakes of nearly the same strength happen close together in time and location — within seconds, minutes or hours. Unlike aftershocks, which are smaller than the main event, both Davao quakes were strong enough to be considered separate main shocks.
However, the magnitude 6.0 earthquake that hit Cagwait, Surigao del Sur, on Oct. 11 was not an aftershock of the Manay doublet and was unrelated to the other tremors.
“That quake was about 200 kilometers away from the Manay events, much farther than the usual aftershock zone that extends only tens of kilometers,” Bacolcol said.
What this means for the public
The clustering of earthquakes underscores the country’s high vulnerability to seismic hazards.
Experts said the Philippines will continue to experience frequent earthquakes because it sits on the Philippine Mobile Belt — a major tectonic boundary constantly under stress from the converging plates on its eastern and western sides.
This continuous pressure means the country’s numerous faults and trenches can move at any time. (DPC)