MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) yesterday raised the status of Bulusan Volcano in Sorsogon to Alert Level 1 or “abnormal” due to increased seismic activity in the past few days.
Phivolcs said Bulusan Volcano’s monitoring network has recorded a total of 53 volcanic earthquakes, including 43 low-frequency events, since July 3 that are associated with weak and shallow hydrothermal or magmatic gas activity within the edifice.
“The increased seismicity could be succeeded by steam-driven or phreatic eruptions at the summit crater or from flank vents on the upper to middle slopes, despite the absence of visible degassing or steaming from the active vent this year,” Phivolcs said in an advisory.
Ground deformation data from continuous GPS or global positioning system measurements also indicated a short-term inflation of the volcano’s edifice since late February, it said.
“These parameters indicate that volcanic processes are underway beneath the edifice that may be caused by deep-seated degassing or hydrothermal activity or magmatic intrusion,” Phivolcs said.
Entry into the four-kilometer radius permanent danger zone is prohibited.