Good news – only 2 volcanoes with Alert Level 1
In their bulletin from April 24, 2011, PHIVOLCS informs that they lowered Bulusan Volcano’s status from Alert Level 1 (abnormal) to Alert Level 0 (normal).
Mount Bulusan in Sorsogon had shown increased activity since November 17, 2010.
PHIVOLCS now lowered the Alert Level to 0 because:
- The frequency of volcanic earthquake occurrences has declined to baseline levels (0-2 events/day), indicating quiescence in the magmatic or hydrothermal system. Short-lived swarms (9-21 events/day) on 25 May, 10 August, 11 September and December of 2011, and 22 January of 2012, have been ascribed to crustal readjustments in the volcanic edifice after the May 2011 phreatic eruption.
- Results of precise leveling at both Inlagadian line on the north-northeastern slope and Mapaso line on the south-southeastern slope indicate that the volcano edifice has deflated since late November 2011. This suggests that no substantial pressure source in the subsurface, which could potentially trigger another eruption, can be detected.
- Steaming activity from the crater and known thermal vents has been frequently weak or wispy compared to the more moderate steam emissions during periods of unrest.
However, the public is reminded to avoid entry into the 4-kilometer Permanent Danger Zone (PDZ) due to the perennial threat of sudden phreatic eruptions and rockfalls on the upper slopes. Furthermore, people living in valleys and along active river channels are cautioned to remain vigilant against sediment-laden streamflows and lahars in the event of heavy and prolonged rainfall.