By: Bennie A. Recebido
SORSOGON
PROVINCE, May 4 – Philippine Institute of Volcanology and Seismology (Phivolcs)
has finally lowered the alert level status of Mt. Bulusan from Alert level 1 or
abnormal to Alert Level 0 or normal. This means that no eruption is foreseen in
the immediate future.
Phivolcs
Bulusan Volcano Observatory resident volcanologist Crispulo Diolata said that
the lowering of the alert level status as stated in Bulusan Volcano Bulletin
dated April 24, 2012, was due the overall decline of the monitoring parameters
after the volcano’s last phreatic (steam-driven) eruption on May 13, 2011 as
supported by the following observations:
(1)
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.
(2)
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.
(3)
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.
He
also said that the bulletin issued on April 24, 2012 will be the last bulletin
to be issued for Bulusan Volcano until new developments in monitoring
parameters occur.
Meanwhile,
in the light of the declaration, Diolata still remind the public 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.