Mt. Bulusan's monitoring network in Sorsogon detected 166 volcanic earthquakes in the past 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Wednesday, May 12.
Phivolcs said that ground deformation data from real-time electronic tilt monitoring recorded sustained inflation of the upper slopes that began on March 6, 2021, which is consistent with the short-term inflation of the edifice measured by continuous GPS monitoring since February 2021.
"These parameters generally indicate that shallow hydrothermal processes are occurring beneath the edifice," it pointed out.
Phivolcs said Bulusan Volcano is under an "abnormal" status thus Alert Level 1 was raised on Tuesday, May 11.
READ: Phivolcs raises Alert Level 1 over Bulusan Volcano
Local government units and the public were advised to prevent from entering the four-kilometer radius permanent danger zone.
Likewise, Phivolcs said the public should remain vigilant when entering the two-kilometer extended danger zone on the southeast sector due to increased possibilities of sudden and hazardous phreatic eruptions.
Civil aviation authorities were also asked to advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft.
Furthermore, people living within valleys and along river/stream channels especially on the southeast, southwest, and northwest sector of the edifice should stay vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should phreatic eruption occur.