There was an increase in the seismic activity in Mount Bulusan in Sorsogon, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Thursday.
In its 10AM bulletin, the state volcanologists recorded 71 volcanic and tectonic earthquakes in Bulusan volcano "associated with rock fracturing" as of 5 AM.
The magnitude of the earthquakes ranged from 0.3 to 2.2.
According to PHIVOLCS, the earthquakes occurred between one to six kilometers beneath the southern flank of the volcano edifice.
Weak to moderate volume plumes were also observed due to the degassing activity from the summit crater and active vents of the volcano.
"The seismic parameters indicate shallow hydrothermal activity is underway and may lead to steam-driven or phreatic eruption," the agency said.
Despite this, PHIVOLCS said Bulusan Volcano still remains under Alert Level 1, which means there is a low-level of unrest with increased chances of steam-driven or phreatic eruptions.
The agency also prohibited the public from entering the four-kilometer radius permanent danger zone and advised them to be vigilant within the two-kilometer extended danger zone on the southeast sector due to possible sudden and hazardous phreatic eruptions.
Pilots should also avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft.
People living within valleys and along river or stream channels must also be vigilant against sediment-laden stream flows and lahars.
The movement of these pyroclastic materials may happen during heavy and prolonged rainfall, especially after a phreatic eruption.
