The Philippine Institute of Volcanology and Seismology (Phivolcs) has detected 105 earthquakes in Mt. Bulusan in Sorsogon within the 24-hour monitoring period from Saturday, June 12, to Sunday, June 13.
Phivolcs also observed a weak emission of white steam-laden plumes from the lower southeast vents before drifting north-northwest.
"Ground deformation data from real-time electronic tilt monitoring recorded sustained inflation of the upper slopes that began on March 6, 2021, consistent with short-term inflation of the edifice measured by continuous GPS monitoring since February 2021," it pointed out.
Phivolcs said that these parameters "generally indicate that shallow hydrothermal processes are occurring beneath the edifice."
Mt. Bulusan's condition is still "abnormal" thus it remains under Alert Level 1.
Its status has been raised from 0 to 1 on May 11, 2021, due to a continuous detection of low-level volcanic unrest early this year.
Local government units and the public were reminded that entry into the four-kilometer radius permanent danger zone is strictly prohibited.
Phivolcs also advised the public to remain vigilant when entering the two-kilometer extended danger zone on the southeast sector due to the increased possibilities of sudden and hazardous phreatic eruptions.