MAYON VOLCANO BULLETIN:

27 November 2012

This serves as notice for the lowering of Mayon Volcano’s status from Alert Level 1 (abnormal) to Alert Level 0 (normal).

Since Alert Level 2 was lowered to Alert Level 1 on 2 March 2010, Mayon Volcano exhibited a general decline of monitoring parameters to normal/baseline values as detailed below, indicating a return to normalcy.

1. The occurrence of micro-earthquakes associated with rock fracturing within the volcanic system has waned to normal baseline levels of 0-5 events/day, while micro-earthquakes and volcanic tremor associated with magmatic activity has consisted only of small discrete sporadic events.

1. Ground deformation monitoring using Precise Leveling (PL) surveys on the northern and eastern flanks, combined with recently emerging patterns in ground tilt monitoring, indicate that minimal ground deformation recorded in Mayon may not be associated with new magmatic intrusion. Slight inflation of the lower northern to eastern slopes has been recorded by PL surveys from June 2011 to November 2012. However, ground tilt recorded by an array on the same sectors for the same period  is not fully consistent with volcanic ground deformation, but rather, more consistent with incremental motion along a nearby segment of the Philippine Fault Zone.

1. Activity associated with shallow degassing magma has waned significantly. Steaming from the crater has varied from moderate, weak to wispy, but is presently more often weak and occasionally wispy. Crater glow has also ceased since March 2012, indicating diminished superheated gas from shallow magma at the vent. These observations are consistent with sulfur dioxide flux measured in the last six months that have fallen below baseline levels of 500 tonnes/day.

In view of the above observations, PHIVOLCS is now lowering the alert status of Mayon Volcano from Alert Level 1 to Alert level 0. This means that no explosive eruption is foreseen in the immediate future. However, the public is still reminded to avoid entry into the 6-km Permanent Danger Zone or PDZ due to perennial hazards of rockfalls, avalanche, ash puffs and steam-driven explosions at the summit area. Furthermore, people living in valleys and active river channels are cautioned to remain vigilant against sediment-laden streamflows and lahars in the event of prolonged and heavy rainfalls.

This will be the last bulletin for Mayon Volcano until new developments in monitoring parameters occur.

DOST – PHIVOLCS