LEGAZPI CITY – The Philippine Institute of Volcanology and Seismology has raised Alert Level 1 over Mount Bulusan in Sorsogon after monitoring systems detected hundreds of volcanic earthquakes over the past week.
Phivolcs reported that the Bulusan Volcano Network recorded 475 seismic events starting March 15, signaling increased volcanic unrest beneath the mountain.
Most of the tremors were classified as weak volcano-tectonic earthquakes, believed to be caused by the cracking of rocks beneath the volcano at shallow depths.
The agency noted that the nature of the recent seismic activity is similar to patterns observed before Bulusan’s eruptions in 2022 and 2025.
Data from ground monitoring equipment also showed inflation or swelling along the volcano’s western and southeastern slopes in recent weeks, indicating movement beneath the volcanic structure.
Meanwhile, degassing activity from Bulusan’s active vents has remained weak to moderate. Sulfur dioxide emissions measured on March 17 averaged 91 tons daily, which is within background levels.
Phivolcs explained that the current conditions point to shallow hydrothermal processes that could eventually trigger steam-driven eruptions at the volcano’s summit vents.
Authorities reminded the public that entry into the four-kilometer permanent danger zone around the volcano remains prohibited.
Residents within the two-kilometer extended danger zone in the southeast sector were urged to stay cautious due to potential hazards such as ashfall, pyroclastic density currents, rockfalls, and ballistic fragments.
Communities west of the volcano were advised to prepare for possible ashfall, while vulnerable groups—including the elderly, pregnant women, infants, and people with medical conditions—should take extra precautions.
Phivolcs also cautioned pilots to avoid flying close to the volcano’s peak, as sudden eruptions may release ash that could threaten aircraft safety.
People living near rivers and streams around the volcano were likewise warned to remain vigilant against lahars and sediment-laden flows, especially during prolonged rainfall.
elamigo/xf
