At least 16 volcanic earthquakes were monitored at Kanlaon Volcano in Negros Island over a 24-hour period, equaling the number recorded from the previous day, state seismologists said Saturday.
In its latest bulletin, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said that of the 16 earthquakes recorded from 12 a.m. Friday until 12 a.m. Saturday, two were volcanic tremors that lasted about eight to 25 minutes.
PHIVOLCS also recorded 16 volcanic earthquakes on Thursday, but logged more volcanic tremors at six. These tremors also lasted longer, with a duration of up to 52 minutes.
State seismologists define a volcanic earthquake as coming from an active volcano and distinguished from each other by their mode of arrivals, periods, amplitudes, and differ in appearance, among other factors. On the other hand, a volcanic tremor is characterized by a continuous seismic signal with regular or irregular sine wave appearance and low frequencies (0.5-5 Hz).
A tremor can be caused by different processes inside the volcano, including resonance triggered by explosions and magma flowing through cracks and vents, or continuous low-frequency earthquakes so closely spaced that they cannot be visually separated.
Kanlaon’s activity continues to indicate “intensified unrest” under Alert Level 3. Magmatic intrusion to shallow levels of the edifice is driving unrest, with indications that a hazardous eruption could occur in weeks.
The volcano edifice remained inflated.
It released 7,705 tons of sulfur dioxide gas, which is higher compared to the 5,756 tons reported in PHIVOLCS’ previous 24-hour bulletin released Friday.
PHIVOLCS has already recommended the evacuation of residents from the six-kilometer radius of the volcano’s summit. Flying any aircraft close to the volcano also remains prohibited.
On December 9, an explosive eruption occurred at the summit vent of Kanlaon Volcano, producing a voluminous plume that rapidly rose to 4,000 meters.
Ashfall was reported and pyroclastic density currents or PDCs descended at the slopes of the volcano.
Last Thursday, the Office of Civil Defense (OCD) said it was preparing for a possible raising of the alert level at Kanlaon Volcano. Officials said they were preparing to establish a tent city in Himamaylan City in anticipation of a “possible escalation.”
Potential hazards from the volcano include sudden explosive eruption, lava flow or effusion, ashfall, PDC, rockfall, and lahars during heavy rains.
The volcano’s danger zone was expanded to a radius of six kilometers from the summit crater or active vent. — VDV, GMA Integrated News
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