The Philippine Institute of Volcanology and Seismology on Tuesday, July 28, warned of increased seismic activity at Bulusan Volcano.
PHIVOLCS issued the warning after Bulusan posted 109 volcanic earthquakes since Tuesday midnight.
It also noted that "degassing" from the active vents has been weak to moderate while low volcanic sulfur dioxide emission of 50 tons per day was measured on July 21.
"These parameters likely indicate active shallow hydrothermal or tectonic processes beneath the volcano which could lead to steam-driven or phreatic eruptions at any of the summit vents," PHIVOLCS said.
PHIVOLCS advised local government units to strictly enforce the ban on the entry into the 4-kilometer radius Permanent Danger Zone.
The public was also told to exercise vigilance in the 2-kilometer Extended Danger Zone in the southeast sector due to the possible impact of volcanic hazards such as pyroclastic density currents, rockfall, avalanches, and others.
Communities south and downwind of the volcano should also prepare for ashfall if a phreatic eruption occurs, PHIVOLCS said, while those living within valleys and along river streams, especially in the western sectors of the edifice, should be vigilant against sediment-laden stream flows and lahar.
"DOST-PHIVOLCS is closely monitoring Bulusan Volcano's condition and any new development will be relayed to all concerned," PHIVOLCS said.
Bulusan remains under Alert Level 1.
