Phivolcs sets 5-meter buffer zone in Bogo active fault

COLLAPSED. A man stands next to a collapsed building in Bogo City on Oct. 1, 2025, after a 6.9-magnitude quake struck off the coast of the central Philippines late Sept. 30. (Photo courtesy: Ted ALJIBE / AFP)

By Brian Campued

The Philippine Institute of Volcanology and Seismology (Phivolcs) has designated a 5-meter buffer zone from both sides of the Bogo Bay Fault, which triggered the magnitude 6.9 earthquake in northern Cebu last week.

In an advisory Monday, the Phivolcs advised the public to avoid building any structure on top or within the buffer zone to avoid the danger of fissuring from the active fault’s movement.

Phivolcs Director Teresito Bacolcol stressed that this also applies to all areas in the country where there is an active fault.

“Kung may bahay na nakatayo on top of an active fault, kahit saan naman sa Pilipinas, basta ang sinasabi natin—dapat walang bahay na tinatayo on top of an active fault,” Bacolcol said iun an interview on Bagong Pilipinas Ngayon.

He added that based on the mapping of the Phivolcs’ Quick Response Team (QRT) both sides of the fault stretches about 6 kilometers on land but a huge part of it is underwater and may stretch up to 40 or 50 km.

On Oct. 3, the Phivolcs’ QRT conducted a field inspection of the powerful Cebu quake and found the onland extension of the Bogo Bay Fault in Sitio Looc, Barangay Nailon in Bogo City.

Bacolcol said the active offshore fault traverses Barangays Nailon, Libertad, and Dakit in Bogo City.

“Patuloy pa rin po ang field verification at magkakaroon din ng offshore studies para makumpleto ang mapping,” Bacolcol said.

The Phivolcs chief also urged the Bogo City government to use the results of the ongoing field mapping to guide its future land use planning (LUP) and preparedness plans to 

“Para po ma-integrate na yung location ng fault and ma-integrate na rin po nila yung presence ng fault sa kanilang LUPs,” Bacolcol said.

As of 11:00 a.m. on Tuesday, a total of 8,298 aftershocks were recorded from the 6.9-magnitude temblor in Cebu. Of this number, 1,556 were plotted while 34 were felt.

Aftershock magnitudes ranged from 1.0 to 5.1.

The northern Cebu earthquake has claimed the lives of 72 individuals and injured 559 others, according to the situational report of the National Disaster Risk Reduction and Management Council (NDRRMC) issued at 6:00 a.m. today.

All of the casualties—both dead and injured—are still undergoing validation, the NDRRMC stated.

Around 165,988 families or equivalent to 611,624 persons were affected by the quake across 211 barangays in Central Visayas.

Meanwhile, the Regional Disaster Risk Reduction and Management Council (RDRRMC) VII (Central Visayas) has also reminded residents living in landslide-prone and geologically unstable areas to immediately evacuate to safer grounds due to the risk of landslides and secondary hazards triggered by the earthquake and persistent rains.

“Aftershocks and saturated soil conditions may further weaken slopes, increasing the likelihood of landslides, rockfalls, and ground subsidence. The safety of all residents remains the highest priority,” the Office of Civil Defense (OCD) Regional Office VII said in a statement.

-jpv

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