THE Philippine Institute of Volcanology and Seismology (Phivolcs) has recorded an increase in seismic activity at the Bulusan Volcano over the past 24 hours.
In an advisory, Phivolcs said 72 volcanic earthquakes were recorded by the Bulusan Volcano Network (BVN) since 12 a.m. of October 11, 2025.
“These volcano-tectonic (VT) earthquakes are associated with rock fracturing and are occurring at depths less than 10 kilometers beneath the northern sector of the volcano. Degassing activity from the active vents ranged from very weak to weak when the volcano was visible for the past days,” Phivolcs said.
The agency said sulfur dioxide or SO2 emission was recorded at an average of 31 tonnes per day as of October 9, which is below the baseline of 200 tonnes per day.
The Phivolcs said these activities indicate shallow hydrothermal activity beneath the volcano.
“Alert Level 1 (low-level unrest) is maintained over Bulusan Volcano, but presently, there are increased chances of steam-driven or phreatic eruptions occurring from the crater and/or its active vents on the summit that could occur suddenly and without warning,” it added.
The agency reminded local government units and residents that entry into the four-kilometer radius Permanent Danger Zone (PDZ) must be strictly prohibited and that vigilance in the two-kilometer Extended Danger Zone (EDZ) on the southeast sector of the volcano must be exercised due to the possible impacts of volcanic hazards, such as pyroclastic density currents or PDCs, ballistic projectiles, rockfall, avalanches, ashfall and others on these danger areas.
The Phivolcs urged the public to take necessary precautions against ashfall by using protective masks or wet cloth to prevent ash inhalation, with special attention given to vulnerable persons, including the elderly, persons with respiratory or cardio-vascular diseases, expecting mothers and infants.
It noted that flying close to the volcano’s summit is prohibited, as ash from any sudden phreatic eruption can be hazardous to aircraft.
“Furthermore, people living within valleys and along river/stream channels especially on the western sectors of the edifice should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should phreatic eruption occur,” said Phivolcs. (TPM/SunStar Philippines)