The Philippine Institute of Volcanology and Seismology has raised the unrest status of Bulusan Volcano in Sorsogon province from Alert Level 0 or normal status to Alert Level 1 or low-level unrest after exhibiting a series of volcanic earthquakes.

In its volcanic bulletin, Phivolcs said the Bulusan Volcano Network has recorded 121 volcanic earthquakes since 14 October, 37 of which were volcano-tectonic tremors that are associated with rock fracturing processes at depths of 1-9 kilometers beneath the northwestern and southern slopes of the volcano edifice.

Phivolcs also observed ground deformation and inflation or swelling of the Bulusan's southern flank since February and the northeastern flank has been swelling since September.

Bulusan also logged an increase in the volcanic carbon dioxide concentration from June to August and the spring temperature also increased since February.