187 quakes shake Mayon – Phivolcs
The Philippine Institute of Volcanology and Seismology recorded a total of 187 volcanic earthquakes in Mayon Volcano on All Saints’ Day.
According to Phivolcs in their 24-hour observation from 5 a.m. on November 1 to 5 a.m. on Thursday, November 2, these include 179 volcanic tremors, each lasting one to 12 minutes.
Phivolcs also logged 175 rockfall events and four Pyroclastic Density Current (PDC) events.
From October 31 to November 1, Mayon had 113 volcanic earthquakes, including 110 volcanic tremors that lasted one to 49 minutes long, along with 133 rockfall events and three PDCS, according to Phivolcs.
Monitoring of the Mayon Volcano Network showed “slow effusion” of lava flow from the crater to lengths of 3.4 kilometers (kms), 2.8 kms, and 1.1 kms on the Bonga, Mi-isi, and Basud gullies, respectively.
A lava collapse up to four kms from the crater was observed.
Monitoring showed that the lava flows have “maintained their advances” to approximately 3.4 kilometers in Bonga (southeastern), 2.8 kilometers in Mi-isi (south), and 1.1 kilometers in Basud (eastern) gullies.
Debris from rockfalls and PDCS resulting from the summit dome collapse remains within a four-kilometer radius of the crater, Phivolcs said.
Meanwhile, it was noted that volcanic sulfur dioxide (SO2) emissions averaged 1,539 tons per day on November 1.
Citing short-term observations from electronic tilt and Global Positioning System monitoring, Phivolcs noted an “inflation of the northwestern upper and middle slopes” since late July 2023 and October 2023, respectively.
“Longer-term ground deformation parameters from EDM, precise leveling, continuous GPS, and electronic tilt monitoring indicate that Mayon is still generally inflated relative to baseline levels,” Phivolcs said.
In light of these developments, Phivolcs maintained Alert Level 3 for Mayon Volcano.
This status indicates that the volcano is currently in a relatively “high level of unrest” and a hazardous eruption within weeks or even days remains a possibility.
Phivolcs strongly recommended that the six-km radius Permanent Danger Zone (PDZ) “remain evacuated” due to the danger of PDCS, lava flows, rockfalls, and other volcanic hazards.
Increased vigilance against PDCS, lahars, and sedimentladen stream flows along channels draining the edifice was advised.
Moreover, Phivolcs noted that heavy rainfall could also “generate channel-confined lahars and sediment-laden stream flows in channels where PDC deposits were emplaced.”
In light of these conditions, Phivolcs advised civil aviation authorities to instruct pilots to avoid flying near the volcano’s summit as ash from a sudden eruption could pose a threat to aircraft.
Phivolcs noted that based on the current prevailing wind pattern, ash fall events may “most likely occur” on the south side of Mayon.