AUTHORITIES recorded only three volcanic earthquakes in Bulusan Volcano in Sorsogon in the latest 24-hour monitoring period but the Philippine Institute of Volcanology and Seismology (Phivolcs) said the alert will not be lowered yet and will remain under Level 1 (low-level unrest).
The three volcanic quakes were recorded by Phivolcs from 5 a.m. on Wednesday to 5 a.m. yesterday. Ten quakes were recorded in the previous 24-hour period.
Bulusan Volcano had a phreatic or steam-driven eruption early morning last Sunday, causing ashfall that affected at least 17 barangays. It had a similar eruption a week earlier.
Phivolcs director Renato Solidum said it is not yet the time to lower the alert to Level 0 (normal).
“It’s just one day and there are other parameters that show it’s not normal. We still have a lot of sulfur dioxide,” he said.
While acknowledging the fewer volcanic quakes is an improvement, Solidum said “it’s just the hydrothermal activity, not as vigorous as the previous day.”
Solidum said the decreasing number of volcanic earthquakes means the volcano is having less hydrothermal activity.
“If the hydrothermal activity is lower, then it will be reflected as lesser steaming and lesser volcanic quakes simply because the quakes are related to hydrothermal activity. The quakes are not related to magma,” said Solidum.
Solidum said Bulusan Volcano will remain under Alert Level 1.
“Still at alert Level 1… We have to assess the character of the volcano daily but then we try to see if it (lesser quakes) will be sustained, if it will be sustained or not,” said Solidum.
Phivolcs, in its latest 24-hour observation report, also said plumes which drifted southwest and west-southwest reached 150 meters, from the previous 500 meters.
Phivolcs said Bulusan Volcano emitted 1,255 tons sulfur dioxide, from the previous 4,625.
