BULUSAN VOLCANO BULLETIN

21 August 2022

06:00 PM

 

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

 

Bulusan Volcano has returned to normalcy following a general decline in monitoring parameters. This is supported by the following observations:

 

1. Volcanic Earthquake Activity:  The frequency of volcanic earthquakes has declined to baseline levels (0-5 earthquakes/day) since the third week of July 2022. This indicates that rock-fracturing within the volcanic edifice associated with shallow hydrothermal activity has diminished.
2. Ground Deformation: Data from continuous GPS measurements and radial tilt indicated short-term inflation of the southeastern edifice of Bulusan Volcano since April 2022. However, long-term ground deformation suggests that this is primarily driven by tectonic processes rather than pressurization from subsurface magma.
3. Gas Emission: Sulfur Dioxide emission or SO₂ flux from Bulusan based on gas spectrometry has declined from an average of approximately 1,900 tonnes/day between 5 and 12 June 2022 to 230 tonnes/day between 25 July and 6 August 2022. The diminishing concentration of SO₂ likely indicates the depletion of volcanic gas input to the active shallow hydrothermal system.
4. Visual Observation of the Summit:  Degassing activity from the active vents has diminished to very weak to moderate emission of steam-laden plumes.

 

In view of the above, PHIVOLCS-DOST is now lowering the alert status of Bulusan from Alert Level 1 to Alert Level 0.  This means observational parameters have returned to baseline or background levels and no magmatic eruption is foreseen in the immediate future. However, in the event of a renewed increase in any one or combination of the above monitoring parameters, the alert status may step up once again to Alert Level 1. The local government units and the public, however, are reminded that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) particularly near the vents on the south-southeastern slopes, should be avoided due to the possibility of sudden and hazardous steam-driven or phreatic eruption, rockfall and landslide. 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 valleys and along river/stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall. DOST-PHIVOLCS is closely monitoring Bulusan Volcano’s condition and any new development will be relayed to all concerned.

 

This will be the last bulletin for Bulusan Volcano until new developments in monitoring parameters occur.

 

DOST-PHIVOLCS