THE magnitude 6.9 earthquake that jolted Cebu Tuesday night, September 30, 2025, was not triggered by a fault line in Bogo City, said Philippine Institute of Volcanology and Seismology (Phivolcs) Director Dr. Teresito Bacolcol.
“Meron tayong Bogo fault pero hindi ito ‘yung nakapag-produce ng earthquake last night. Ang Bogo fault nasa lupa, ito, ‘yung nag-produce ng earthquake last night, was offshore nasa dagat so magkaiba po sila,” he said in a phone interview with SunStar on Wednesday, October 1, 2025.
(We have the Bogo Fault, but that was not the one that produced the earthquake last night. The Bogo Fault is on land, while the one that produced the earthquake last night was offshore, in the sea, so they are different.)
Bacolcol said while there were instances where a movement of a fault can be triggered by a jolt from another area, the distance should be at least five kilometers.
“The faults have to be very close to each other around five kilometers ‘yung distance. Ito naman kasi malayo ito, but pwede pong mangyari if magkalapit sila, so as I mentioned, malayo ang epicenter na nasa dagat,” he added.
(The faults would have to be very close to each other, with a distance of around five kilometers. In this case, they are far apart, but it could happen if they were near each other. As I mentioned, the epicenter is far away, located offshore.)
A magnitude 6.9 earthquake hit Cebu province on Tuesday evening, with the epicenter located 21 kilometers northeast of Bogo City in northern Cebu.
Bacolcol said it was a “strong earthquake” considering its shallowness with a depth of only five kilometers.
“Usually kasi ‘yung seismic energy as it travels towards the surface, humihina. Ngayon kung malalim ang pinanggalingan ng seismic energy natin habang nagta-travel towards the surface, humihina na pagdating sa ibabaw, nawawalan ng lakas. Now ditto, five kilometers nagstart as it travels towards the surface, hindi pa niya masyado nareduce ang energy niya, so pagdating sa ibabaw, malakas pa rin ang energy kaya malaki ang damage,” he said.
(Usually, seismic energy weakens as it travels toward the surface. If the origin of the seismic energy is deep, by the time it reaches the surface it has already lost much of its strength. But in this case, since it started just five kilometers deep, the energy was not significantly reduced as it traveled upward. So when it reached the surface, the energy was still strong, which is why the damage was severe.)
Bacolcol also clarified that there is no connection between the magnitude 6.9 earthquake in Bogo City and the minor eruption of Taal Volcano in Batangas early Tuesday dawn.
“Wala naman connection yan kasi we have 24 active volcanoes, and we also have 180 active fault segments spread all over the country, so there is always a chance, possibility na magkasabay-sabay yan,” he added.
(There’s no connection between them because we have 24 active volcanoes and about 180 active fault segments spread across the country, so there is always a chance or possibility that they could occur at the same time.)
The Taal Volcano erupted around 2 a.m. but it remained under Alert Level 1 or low-level unrest. (TPM/SunStar Philippines)