BULUSAN VOLCANO ADVISORY

25 October 2023

03:00 PM

This serves as a notice for raising the alert level status of Bulusan Volcano from Alert Level 0 (Normal) to Alert Level 1 (Low-level of Unrest).

Bulusan Volcano entered a period of low-level unrest with a sustained series of volcanic earthquakes that began on 14 October 2023. Since then, a total of one hundred twenty-one (121) volcanic earthquakes have been recorded by the Bulusan Volcano Network (BVN). Of these, thirty-seven (37) were volcano-tectonic earthquakes that are associated with rock fracturing processes at depths of 1 to 9 kilometers beneath the northwestern and southeastern slopes of the volcano edifice. In addition to this, ground deformation data from electronic tilt and GPS monitoring respectively indicate inflation or swelling of the southern flank since February 2023 and of the northeastern flank since September 2023. A notable increase of volcanic carbon dioxide (CO₂) concentrations from June to August 2023 and spring temperature since February 2023 was detected in a monitored spring on the southwestern slopes. These parameters indicate that hydrothermal activity driven by deep-seated magma degassing may be occurring beneath the volcano and may lead to steam-driven eruptions at any of its summit vents.

In view of the above, DOST-PHIVOLCS is now raising the alert status of Bulusan Volcano from Alert Level 0 to Alert Level 1, which means that the volcano is currently in a state of low-level unrest. Local government units and the public are reminded that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) should be prohibited and that vigilance in the 2-kilometer Extended Danger Zone (EDZ) in the southeast sector must be exercised due to increased possibilities of sudden and hazardous phreatic eruptions from the summit crater and/or lateral vents. Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft. Furthermore, people living within the valleys and along rivers/stream channels, especially on the southeast, southwest, and northwest sectors of the edifice should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should a phreatic eruption occur. DOST-PHIVOLCS is closely monitoring Bulusan’s condition, and any new development will be communicated to all concerned stakeholders.

DOST-PHIVOLCS