Sorsogon: An increase in seismic activity has been observed in Bulusan Volcano, the Philippine Institute of Volcanology and Seismology (Phivolcs) said Monday. In an advisory, the Phivolcs reported that 49 volcanic earthquakes were recorded from 3 a.m. of February 26 until 11 a.m. of March 2. Of these, 16 were volcano-tectonic earthquakes associated with rock fracturing between three to six kilometers beneath the northern and southeastern edifice of the volcano.
According to Philippines News Agency, the increased seismicity may indicate that hydrothermal processes beneath the volcano are underway and may lead to sudden steam-driven or phreatic eruptions. "This happens when there is an interaction with water and hot volcanic materials, which can cause rock fracturing and result in volcanic earthquakes," Phivolcs Director Teresito Bacolcol said.
Bacolcol warned that the increased seismicity also increases the likelihood of a sudden steam-driven or phreatic eruption, which can happen with little or no warning, especially in areas near the active vents. All other monitoring parameters, meanwhile, have remained in the background levels.
Degassing activity from the summit crater and active vents has been very weak to moderate for the past days. Sulfur dioxide emission from the summit vents has been too weak to be detected during the last measurement on February 26.
Alert Level 0 is maintained over Bulusan Volcano, which means that no magmatic eruption is foreseen. However, the public is reminded that entry into the four-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 eruptions, rockfall, landslides, and other related volcanic hazards.
Phivolcs added that local government units should prepare their response and revisit emergency plans in case the volcano's alert status is raised to Level 1. Aviation authorities are also urged to advise pilots to avoid flying close to the volcano's summit, as ash from any sudden phreatic eruption can be hazardous to aircraft.
