The Philippine Institute of Volcanology and Seismology (Phivolcs) has lowered the alert status of Mount Pinatubo to Alert Level 0 or “normal” following the continued decline of seismic activity observed in the vicinity of the volcano.
In an advisory issued Thursday, Aug. 12, state seismologists said a total of 104 volcanic earthquakes or an average of 2-3 events per day were recorded by the Pinatubo Volcano Network from July 1 to Aug. 11.
This is a significant decrease compared to the period from Jan. 28 to June 30 when earthquake activity averaged 12 to 13 events per day and ranged in strength from magnitude 0.7 to 3.2, it noted.
Moreover, the agency said diffuse carbon dioxide (CO2) flux from the Pinatubo Crater lake was measured at 263 tonnes per day in mid-April, an indication of deep magma degassing.
It added that data collected from the monitoring of the Pinatubo edifice that began in March indicate that ground deformation is likely tectonic, rather than volcanic, in origin.
“In view of the above, PHIVOLCS-DOST is now lowering the alert status of Pinatubo Volcano from Alert Level 1 to Alert Level 0. This means observational parameters have returned to baseline levels and the volcano has returned to a period of quiescence,” the agency said.
“However, in the event of a renewed increase in any one or combination of the above monitoring parameters, the alert status may step up once again to Alert Level 1,” it added.
Phivolcs warned that entry into the Pinatubo Crater area must always be conducted with caution due to the perennial hazards of rockfalls, landslides and expulsions of lethal volcanic CO2.
Likewise, people living in valleys and active river channels are cautioned to remain vigilant against sediment-laden streamflows and lahars in the event of prolonged and heavy rainfall.
Mt. Pinatubo was placed under Alert Level 1 or “low-level unrest” in March due to persistence of seismic activities.