MANILA - The Philippine Institute of Volcanology and Seismology (Phivolcs) has recorded increased seismic activity at Bulusan Volcano in Sorsogon.

According to its advisory released Monday night, a total of 94 volcanic earthquakes were recorded in the Bulusan Volcano area since April 12, 2024.

Of this number, 90 were weak and shallow volcanic-tectonic earthquakes, and 4 were low frequency volcanic earthquakes.

Phivolcs also said the slight increase in volcanic earthquake activity could be caused by “hydrothermal activity, which could lead to short-term pressurization of the edifice.”

Degassing activity, on the other hand, has been very weak to moderate.

Alert Level 0 (Normal) remains hoisted over Bulusan Volcano, but Phivolcs warned that there are chances of steam-driven or phreatic eruptions from the crater and/or its active vents on the summit that could occur suddenly and without warning.

Phivolcs reminded local government units and the public that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) should be prohibited, especially near the vents on the south-southeastern slopes due to “possible threat of sudden volcanic hazards such as rockfall, landslide, ballistic projectiles, small pyroclastic density currents or “uson” and others.”

The Phivolcs uses a 5-level alert system for volcanoes.

Bulusan has been under Alert Level 0 since November 2024, after it was placed under Alert 1 from October 2023.