MANILA, Philippines — Increased seismic activity has been monitored anew in Bulusan Volcano in Sorsogon.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said 91 volcanic-tectonic earthquakes were recorded on Monday.
The quakes, which were associated with rock fracturing, have been observed two to four kilometers beneath the southwestern flanks since 1:38 a.m. on Monday.
“Increased seismic activity and pressurization of the volcano edifice may indicate that hydrothermal processes may be occurring beneath the volcano and may lead to steam-driven eruptions at any of the summit vents,” Phivolcs said.
Bulusan remains under Alert Level 1, which means low-level unrest.
Phivolcs said this means there are also increased chances of steam-driven or phreatic eruptions.
State seismologists said inflation at the southwestern and southeastern flanks of the volcano has been monitored since February last year.
However, Phivolcs said degassing activity from the summit crater and active vents has been very weak to moderate.
It said entry into the four-kilometer-radius permanent danger zone should be prohibited while vigilance must be exercised within the two-kilometer extended danger zone.
The agency warned residents along river and stream channels of sediment-laden stream flows and lahar during heavy rain.
Bulusan’s alert level was raised on Oct. 25 last year due to a sustained series of volcanic earthquakes and an increase in volcanic carbon dioxide concentrations.