MANILA — State seismologists on Monday raised the alert status of Bulusan Volcano to Level 1, or “abnormal," after 53 volcanic earthquakes were recorded since Friday.
“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 a bulletin.
Phivolcs said of the 53 quakes, 43 are “low frequency events that are associated with weak and shallow hydrothermal or magmatic gas activity within the edifice.”
According to the Alert Level status of Bulusan, level 1 or ‘low level of volcanic unrest" indicates a slight increase in volcanic earthquake and steam or gas activity.
Phivolcs said hydrothermal, magmatic, or tectonic disturbances were also recorded. The source of activity was shallow, near crater or in the vicinity of Irosin Caldera, it added.
“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.
The state seismologist bureau has advised against entry into the 4-kilometer radius Permanent Danger Zone (PDZ) while vigilance must be exercised in the Extended Danger Zone (EDZ) "due to the increased possibilities of sudden and hazardous phreatic eruptions."
"Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft," Phivolcs said.
"Furthermore, people living within valleys and along river/stream channels especially on the southeast, southwest and northwest sector of the edifice should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall."