'Is Mt. Apo waking up?' Phivolcs responds to claims on 'link' between Mindanao quakes, volcano

Kristine Sabillo, ABS-CBN News

Posted at Dec 16 2019 08:20 PM

MANILA—The Philippine Institute of Volcanology and Seismology (Phivolcs) on Monday dismissed claims that the recent 6.9-magnitude earthquake to hit Mindanao was caused by Mt. Apo, the country's highest mountain. 

This is after some worried netizens posted on social media, asking if Mt. Apo, which is a potentially active stratovolcano, is "waking up."

An online article, written by a "science writer and geoscientist," suggesting links between the earlier earthquakes and volcanic activity, has also been circulating.

This is not the first time that the institute has had to clarify the status of Mt. Apo, which is a potentially active stratovolcano. 
Mt. Apo is located between Davao City, Davao Del Sur, and Cotabato province. 

However, Ishmael Narag, officer-in-charge of Phivolcs’ Seismological Observation and Earthquake Prediction Division, said such concerns are understandable. 

“Because if you look at the epicenters after the 6.5 (-magnitude earthquake that struck in October), there were a lot of epicenters in the area (near Mt. Apo),” Narag said.

In the aforementioned online article, the author quoted a geophysicist who suggested that the earthquakes "seem to be propagating toward volcanoes Mount Apo and Mount Talomo."

But Narag said the quakes “do not show the same migration of clusters” or patterns seen when Mt. Pinatubo, an active volcano north of Manila, erupted.

Narag said, in the case of Mt. Pinatubo, Phivolcs observed a cluster of small earthquakes that were moving towards the edifice or main portion of the volcano. “You really know that something is off and is related to the volcano.”

On the other hand, the recent quakes were “nearly linear” or around the area of the fault lines, he said.

Cotabato Fault System and other major faults in the area of the recent earthquakes. The last 6.9-magnitude earthquake is believed to have been generated by the Tangbulan Fault. Graphic by Pam Ramos, ABS-CBN News. Source: Phivolcs

Narag assured the public that they have instruments at Mt. Apo to monitor its status. “Of course, we don’t discount the possibility that there could be an eruption of Mt. Apo because it’s still considered potentially active,” he said.

Can the series of major earthquakes in Mindanao actually trigger the eruption of Mt. Apo?

“We have to see the data,” Narag replied. 

Narag said there have been cases of earthquakes causing eruptions but there are also quakes that have stopped volcanic eruptions. 

“But it’s very inconclusive, those earthquake-triggered volcanic eruptions,” he said, adding that it might only happen when the volcano is in the “compressional field” or areas where tectonic plates are being compressed.

“That’s their theory. That it could probably trigger some faults that can induce percolation inside the volcano,” Narag explained. 

Narag said that while they are studying how the series of earthquakes in Mindanao since October are related, people should not think it is something else than a random natural phenomenon.

“It’s not an act of God that is meant to punish people,” he said. “It’s just that there are active faults…When and where they (earthquakes) will occur along the active faults is a toss of a coin.”