MANILA, Oct. 25 (Xinhua) -- The Philippine Institute of Volcanology and Seismology on Wednesday afternoon raised the alert level over Bulusan volcano in Sorsogon province, southeast of Manila, from zero to 1 after it has recorded 121 volcanic earthquakes since Oct. 14.

"It means that the volcano is currently in a state of low-level unrest," the institute said in an advisory.

Of the 121 volcanic earthquakes, the institute said 37 were volcano-tectonic earthquakes associated with rock fracturing processes at depths of one to nine km beneath the northwestern and southeastern slopes of the volcano edifice.

The institute also observed inflation of swelling of the volcano's southern flank since February and of the northeastern flank since September. A notable increase in volcanic carbon dioxide concentrations from June to August was also observed. It detected spring temperature on the southwestern slopes in February.

"These parameters indicate that hydrothermal activity driven by deep-seated magma degassing may be occurring beneath the volcano and may lead to steam-driven eruptions at any of its summit vents," the institute added.

The institute warned the people to stay away from a four-km radius danger zone. It also urged vigilance in the two-km extended danger zone on the southeast sector due to the increased possibilities of sudden and hazardous phreatic eruptions.

Bulusan volcano is 70 km southeast of the Mayon volcano, the most active Philippine volcano in Albay province. Mt. Mayon has been quietly erupting since June this year and continues to be on alert 3 on a scale of 5, with a "potential explosive activity." Enditem

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