PHIVOLCS: Over 440 earthquakes logged at Bulusan Volcano

Over 440 volcano-tectonic earthquakes have been recorded at Bulusan Volcano since May 18 amid its increase in seismic activity, the Philippine Institute for Volcanology and Seismology (PHIVOLCS) said on Wednesday.

“A total of four hundred forty-two (442) volcano-tectonic earthquakes associated with rock fracturing have been recorded by Bulusan Volcano Network (BVN) since 04:00 PM, 18 May 2026. Of these, fifty-five (55) were located less than 5 kilometers beneath the Bulusan Volcano edifice,” PHIVOLCS said in a volcano advisory posted on its Facebook page.

State volcanologists noted that degassing activity from the active vents have been “very weak to moderate” for the past few days.

A low average emission rate of 121 tonnes a day was last recorded on April 22.

PHIVOLCS also observed ground swelling of the northern and upper western slopes of Bulusan Volcano since June 2025 and January 2026, respectively.

“These parameters may indicate slow pressurization of the edifice due to shallow hydrothermal or tectonic processes beneath the volcano that could lead to steam-driven or phreatic eruptions at any of its summit vents,” it said.

Alert Level 1 or low-level unrest is in effect over Bulusan Volcano.

PHIVOLCS warned that increased seismic activity could mean higher chances of phreatic eruptions from any of its summit vents.

“Local government units are advised to strictly prohibit entry into the 4-kilometer radius Permanent Danger Zone (PDZ) and exercise vigilance in the 2-kilometer Extended Danger Zone (EDZ) on the southeast sector 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,” it said.

Those in communities west and downwind of the volcano were told to prepare for possible ashfall if phreatic eruption occurs.

Those living within valleys and river or stream channels were advised to watch out for sediment-laden stream flows and lahars in case of heavy and prolonged rainfall.

Civil aviation authorities were told to remind pilots to “avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft.” — JMA, GMA News