The Philippine Institute of Volcanology and Seismology has observed increased seismic activity in Bulusan Volcano in Sorsogon province.
Phivols has recorded 87 volcanic earthquakes in the Bulusan Volcano Network since 5 a.m. on 14 October. Of the number, 29 were volcano-tectonic or VT earthquakes—associated with rock fracturing processes occurring 1 to 8 kilometers beneath the southern and western sectors of Bulusan Volcano.
The degassing at the active summit crater and vents has been weak to moderate this week.
Bulusan emitted an average of 241 tons of volcanic sulfur dioxide (SO2) gas daily on 19 October.
Phivolcs also noted an increase in volcanic carbon dioxide concentrations from June to August 2023.
The volcanic spring temperature has likewise increased since February. It was detected in a monitored spring on the southwestern sector of the edifice.
Phivolcs said these parameters indicate that hydrothermal activity driven by deep magma degassing may be occurring beneath the volcano and may lead to steam-driven eruptions at any of the summit vents.
Bulusan remains under Alert Level 0 (normal).
However, increased chances of steam-driven or phreatic eruptions occurring at the crater or summit area is still expected.
Entering into the 4-kilometer radius Permanent Danger Zone, 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.
Flying close to the volcano’s summit should also be avoided as ash from any sudden phreatic eruption can be hazardous to aircraft.
Phivolcs also warned people living within valleys and along river or stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall.