‘Weak explosion signal’ recorded at Mt. Pinatubo — PHIVOLCS

A weak explosion signal was reported at Mount Pinatubo on Tuesday afternoon, "which is not a typical known volcanic process," according to PHIVOLCS.

In an advisory, PHIVOLCS said the recent explosion signal is still being evaluated.

"The Pinatubo Volcano Network recorded seismic and infrasound signals of a weak explosion at Mt. Pinatubo between 12:09 PM and 12:13PM," said PHIVOLCS.

"The seismic and infrasound signals are not typical of known volcanic processes and are currently being evaluated together with other potential sources, e.g. aircraft activity, ordnance disposal, and others," state seismologists added.

PINATUBO VOLCANO ADVISORY
30 November 2021
4:00 PM #PinatuboVolcano pic.twitter.com/42v65uKBLS

— PHIVOLCS-DOST (@phivolcs_dost) November 30, 2021

Further, PHIVOLCS reported that there has been a very low seismic activity in the past days at the volcano.

It also reported that in November 2021, the Pinatubo Center Lake's geochemical survey yielded "low diffuse volcanic CO2 flux (257 tonnes/day), discounting magmatic activity beneath the edifice."

In an interview over Super Radyo dzBB, PHIVOLCS chief Renato Solidum said they are still probing the incident as they have not detected ashfall in the Pinatubo area.

"Sa nasabing report wala naman pong nagreport na bumagsak ang abo sa kanilang lugar,"  said Solidum.

(In the report there is no reported ashfall in the area.)

"'Yun po ang ating tinitignan kasi mataas talaga ang ulap sa Pinatubo at makulimlim talaga po... Pero gusto rin namin malaman kung ano ba talaga kasi ngayon' di ko masasabi kung ano talaga yun kasi interpretation din nila yun. Pero sa ground, wala pa kaming nakikitang ash na bumabagsak or na-report," he added.

(We are still looking into that because it is shady there. But we really want to know what the incident is. For now, I really don't know yet because that is their interpretation. But on the ground, we have not seen an ashfall.)

With this, PHIVOLCS warned public to halt traveling to the vicinity of the Mount Pinatubo.

It also advised local government units to ban entry into Pinatubo Crater until authorities have determined the source of the explosion.

PHIVOLCS also advised communities and LGUs surrounding the volcano to be ready for possible earthquake and volcanic hazards.

"Communities and local government units surrounding Pinatubo are reminded to be always prepared for both earthquake and volcanic hazards and to review, prepare and strengthen their contingency, emergency and other disaster preparedness plans," said PHIVOLCS.

"DOST-PHIVOLCS continues to strengthen its monitoring of the volcano with ongoing upgrades to the PVN (Pinatubo Volcano Network), periodic geochemical surveys of the Pinatubo Crater lake and GPS and satellite analysis of ground deformation," it added.

No big explosion yet

Solidum also explained that they are still investigating the source of the weak explosion signal, adding that an aircraft could have possibly triggered the signal, which was detected through a satellite.

"Sa signal kasi hindi 'yun typical phreatic eruption so naghahanap kami kung ano ang explanation kung bakit may signal na 'yan. Usually, 'yung signal na nakikita namin sa earthquake posibleng may helicopter kung mayroon, may nangyaring pagpapalipad ng mga aircraft sa Pinatubo," said Solidum.

(The signal isn't a typical phreatic eruption so we are still finding an explanation on what's behind the signal. Usually, signals we sometimes think are earthquakes could have possibly been made by a helicopter that flew over Pinatubo or an aircraft that was within the area.)

Asked how will PHIVOLCS confirm if there is an aircraft detected in the Pinatubo area, Solidum said, "Tinatanong pa namin sa OCD (Office of the Civil Defense) yan. Kinoconfirm pa namin."

(We are asking with the OCD.)

Solidum also said there was no big explosion that occurred at the Pinatubo Volcano.

"Kung sinabi naman nila walang (aircraft) e may signal nga pero as to explosion na malaki, wala pong ganoong explosion. Masyadong mahina ang signal. (If they said there is no aircraft then there is a signal but on whether there is a big explosion, there is none. The signal is too weak.)," he said.

In addition, Solidum said Pinatubo Volcano is currently under Alert Level 0, adding that there is no reason yet to raise the alert level.

"Wala po kasi kung sakaling may activity ang volcano kung maliit lang po yun, hindi related sa magma iyan. Puwedeng phreatic explosion pero vine-verify pa po natin yun," he explained.

(There is no reason yet because if there is activity at the volcano, it is weak and is not related to magma. It could be a phreatic explosion but we are still verifying that.)

Under Alert Level 0 or normal level, PHIVOLCS said there will be "no major eruption in the foreseeable future." — RSJ, GMA News