Increased seismic activity seen in Bulusan Volcano

MANILA, Philippines — The Philippine Institute of Volcanology and Seismology yesterday reported heightened seismic activity in Bulusan Volcano in Sorsogon, as Phivolcs data showed 72 volcanic earthquakes in the past 24 hours.

In its 9 a.m. advisory, Phivolcs said the earthquakes, classified as volcano-tectonic events, were caused by rock fracturing beneath the northern sector of the volcano at depths of less than 10 kilometers.

Degassing activity in the active vents was described as “very weak to weak,” while sulfur dioxide emissions averaged 31 tons per day on Oct. 9, which is below the baseline level of 200 tons per day.

“These parameters indicate shallow hydrothermal activity beneath the volcano,” Phivolcs said.

Despite the uptick in activity, Phivolcs raised only Alert Level 1 or low-level unrest over Bulusan Volcano – an alert that means “abnormal condition but no eruption is imminent.”

Authorities reiterated the strict prohibition of entry into the four-kilometer permanent danger zone, and urged vigilance within the two-kilometer extended danger zone on the volcano’s southeast sector due to possible hazards such as pyroclastic density currents, rockfall, ashfall and ballistic projectiles.

“Communities that experience ashfall must take all necessary precautions and use protective masks or wet cloth to prevent ash inhalation, especially for vulnerable groups such as the elderly, persons with respiratory or cardiovascular diseases, expecting mothers and infants,” Phivolcs said.

The agency also advised civil aviation authorities to warn pilots against flying close to the summit due to potential ash hazards. It urged residents living near rivers and streams on the western slopes to be alert for possible lahars if heavy rainfall occurs following a phreatic eruption.