MANILA - State seismologists on Tuesday night raised Alert Level 1 over Mt. Bulusan in Sorsogon after detecting "sustained inflation" on the volcano's upper slopes since early March, signaling "volcanic processes."
In a bulletin, Phivolcs said it has recorded a total of 124 volcanic earthquakes there since Saturday.
"The increased seismicity could be followed by stream-driven or phreatic eruptions at the summit crater or from flank vents on the upper to middle slopes," Phivolcs explained in the advisory.
"Ground deformation data from real-time electronic tilt monitoring has been recording sustained inflation of the upper slopes that began Mar. 6, 2021, consistent with short-term inflation of the edifice measured by continuous GHPS monitoring since February 2021."
These developments, the agency said, means that there are volcanic processes "underway beneath the edifice" which were supposedly caused by "shallow hydrothermal activity," a reason for raising the volcano to the Alert Level 1 or "low-level unrest" status.
This also means that Bulusan Volcano is currently in an "abnormal" condition, according to the state volcanologists.
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The agency also reminded the local government units and the residents there that the entry to the 4-kilometer radius permanent danger zone "must be strictly prohibited."
"Vigilance in the 2-kilometer extended danger zone on the southeast sector must be exercised due to the increased possibilities of sudden and hazardous phreatic eruptions," warned Phivolcs.
Phivolcs said it would continue to monitor volcanic activity.
The agency lifted Alert Level 1 from the Sorsogon volcano in late January last year.
Before this, Mt. Bulusan had shown activity in recent years, including an ash explosion in 2016.