The Philippine Institute of Volcanology and Seismology (Phivolcs) on Thursday, March 4, raised Alert Level 1 over Mount Pinatubo in Central Luzon after 25 years due to persistence of seismic activities.
Phivolcs said the Pinatubo Volcano Network (PVN) has detected a total of 1,722 imperceptible earthquakes beneath the Pinatubo edifice since January.
Due to the persistence of seismic activity, Phivolcs said it has raised the status of Pinatubo Volcano from Alert Level 0 to Alert Level 1.
“This means that there is low-level unrest that may be related to tectonic processes beneath the volcano and that no imminent eruption is foreseen,” the agency said.
Phivolcs said the volcano, which is part of the Zambales Mountain Range located on the boundaries of Pampanga, Tarlac, Zambales and Bataan, has been on Alert Level 0 or “normal” status since January 1996.
State seismologists recorded the first cluster of earthquakes from January 20 to 26 along the Sacobia Lineament at depths of 15 to 28 kilometers and ranged between 1.0 and 2.5 in magnitudes.
“This has been succeeded by a more persistent cluster of earthquakes occurring along a north-northwest-south-southeast-trending structure 10 to 35 kilometers beneath the center of the edifice itself, with a few shallower earthquakes occurring on both ends of the cluster,” Phivolcs said.
The said tremors ranged between magnitude 0.5 and 2.8, and are associated with “rock-fracturing processes.”
Moreover, measurements conducted at Pinatubo Crater lake in February yielded a total carbon dioxide flux of 378 tonnes per day, which is still within the background range of 1,000 tonnes per day recorded in the past decade.
Slight increases in the temperatures of monitored fumaroles or gas vents were also recorded, but other characteristics such as acidity remain unchanged.
With this, Phivolcs advised those entering the Pinatubo Crater area must observe with extreme caution and should be avoided if possible.
Communities and local government units surrounding Pinatubo are also reminded to be prepared for both earthquake and volcanic hazards.
Phivolcs has also urged them to review, prepare and strengthen their contingency, emergency and other disaster preparedness plans.
Mount Pinatubo last erupted on June 15, 1991.
The eruption, which is considered as “the second largest volcanic eruption of the 20th century,” reportedly killed more than 840 people.