BULUSAN Volcano in Sorsogon yesterday was placed by the Philippine Institute of Volcanology and Seismology (Phivolcs) under Alert Level 1 due to “low-level unrest.”
Phivolcs said they recorded a total of 126 weak and shallow 0-5 km-deep volcanic earthquakes since 5 a.m. on Tuesday.
Most of these events occurred in the northwestern sector and the summit area of Bulusan and are attributed to rock-fracturing processes within the edifice.
Several monitored parameters indicate increased hydrothermal activity and overall unrest, Phivolcs said.
According to Phivolcs, the ground deformation data from continuous GPS measurements and radial tilt indicate a short-term inflation of the southern flanks of Bulusan Volcano since April 2022.
“Moreover, a pronounced and ongoing inflationary trend that began in late September 2022 was detected by most of the electronic tilt stations on the southwestern and southern slopes. This current inflation cycle signifies ongoing pressurization of the shallow hydrothermal system,” it said.
The Agency also observed that the volcanic carbon dioxide concentrations measured monthly in springs on the southeastern sector of Bulusan Volcano have been increasing since July 2022, with increasing spring temperature since April 2022 in monitored hot springs on the southwestern sector.
Residents at Sitio Talistison, Brgy. Mapaso in Irosin and Bgy. San Roque in Bulusan reported a “sulfurous odor” on Oct. 10 to 11.
However, Phivolcs pointed out that “only very weak to moderate emission of steam-laden plumes is transpiring at the summit crater and northwest vents.”
“Phivolcs is now raising the alert status from Alert Level 0 to Alert Level 1, which means that the volcano is currently in a state of low-level unrest,” the agency said.
Local government units and the public were reminded that entry into the four-kilometer radius permanent danger zone is strictly prohibited.
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