LEGAZPI CITY-Mount Bulusan is again showing signs of restiveness as a dozen earthquakes shook the volcano in Sorsogon province over the last two days and its swelling edifice meant pressure could be building up in its vents, the Philippine Institute of Volcanolgy and Seismology (Phivolcs) said on Wednesday.
Over the last 48 hours, Phivolcs recorded eight volcanic quakes overnight until 8 a.m. on Tuesday and four more quakes overnight until 8 a.m. on Wednesday, according to the agency's bulletins on July 28 and 29.
The Philvocs Precise Leveling Surveys and Global Positioning System (GPS) indicated very slight inflationary trend at the volcano's edifice, according to Eduardo Laguerta, Phivolcs resident volcanologist here.
Alert Level 1 (abnormal) remains hoisted over the volcano.
The public was warned to keep off the 4-kilometer permanent danger zone due to the possibility of sudden and hazardous steam-driven or "phreatic" eruption.
The Phivolcs bulletin advised pilots to avoid flying close to the volcano's summit as ash from any sudden eruption could be dangerous to aircraft.
It warned residents living within valleys and along river channels around the volcano of possible flooding and lahar flows in case of heavy and prolonged rains.
A recent Phivolcs survey discovered a significant volume of lahar deposits along its slopes that could trigger a lahar flow during heavy rainfall.
The Office of Civil Defence (OCD) in Bicol said the volcano had recorded at least seven steam-driven explosions since June, with ash columns rising as high as 1.5 km and affecting villages along the slopes of the volcano in the towns of Bulusan, Juban and Irosin.
OCD and health officials had earlier provided face masks to residents in areas experiencing ash falls and attended to some villagers who had complained of respiratory ailments from ash inhalation.