The Philippine Institute of Volcanology and Seismology (Phivolcs) on Saturday, September 6, recorded 26 volcanic earthquakes in Mayon Volcano, warning that unrest beneath the edifice could trigger sudden steam-driven eruptions.

The agency said that the tremors, detected from 12 a.m. to 5:30 p.m., had magnitudes of ML0.4 to ML2.7 and originated 5 to 10 kilometers deep on the volcano’s northeast flank.

“Mayon has been exhibiting non-uniform inflation or swelling in its northeastern sector since October 2024 and its south to southwestern sectors since March 2025 based on continuous GPS, electronic tilt and EDM ground deformation data,” Phivolcs said in its latest advisory.

The agency said sulfur dioxide emissions remain near baseline levels, averaging 430 tonnes per day this year.

It added that its most recent measurement on September 3 registered at 609 tonnes.

Phivolcs explained that the combination of increased quakes and sustained inflation of the volcano suggests possible magma intrusion, raising the possibility of phreatic activity.

The agency stressed that Mayon remains under Alert Level 1, which signals abnormal activity but no imminent magmatic eruption. Still, it warned the public to stay away from the six-kilometer radius Permanent Danger Zone (PDZ).

“The public is strongly advised to refrain from entering the 6-kilometer radius Permanent Danger Zone (PDZ) due to life-threatening hazards such as rockfall, landslides/avalanches, ballistic projectiles and short pyroclastic density currents (PDCs) or ‘uson’ that could be generated by a sudden phreatic eruption from the summit,” the advisory stated.

Also, the agency urged residents to avoid river channels and lahar-prone areas, especially during heavy rains. 

It also told aviation authorities to advise pilots not to fly close to Mayon’s summit as sudden explosions may endanger aircraft.