BACOLOD City – A total of 45 volcanic earthquakes were recorded at Mount Kanlaon on Negros Island in more than 10 hours.
According to the Philippine Institute of Volcanology and Seismology (Phivolcs), volcano-tectonic earthquakes were detected between 12 midnight on Tuesday, January 13, and 10:31 a.m. on January 14, with magnitudes between 0.6 and 3.9.
The strongest earthquake recorded, with a magnitude of 3.9, struck at 4:06 a.m. at a depth of 10 kilometers. Its epicenter was located about nine kilometers north-northeast of La Carlota City, Negros Occidental. Phivolcs said instrumental intensity reached Intensity V in La Carlota City while Intensity II was recorded in Bacolod City. Bago City as well as Canlaon City, Negros Oriental also reportedly felt intensities.
Volcano-tectonic earthquakes, Phivolcs said, are caused by rock fracturing beneath the volcano, a process commonly associated with rising magma or magmatic gases forcing their way toward the surface. The recent increase in these events “strongly indicates progressive rock-fracturing beneath the volcano,” it said.
Moreover, volcanic gas measurements also point to ongoing unrest. Sulfur dioxide (SO₂) emissions from Kanlaon’s summit crater averaged 1,248 tonnes per day based on campaign measurements conducted on January 13. While this figure is close to the medium-term average of 1,767 tonnes per day since the start of the year, emissions earlier peaked at 4,126 tonnes per day on January 9.
“These volcanic earthquakes indicate magma intrusion or the ascent of magma beneath the volcano, which could eventually lead to an eruption, although we cannot determine exactly when,” explained Resident Volcanologist Mari-Andylene Quintia of the Phivolcs Kanlaon Volcano Observatory in La Carlota City.
She noted that in some cases, such as in 2020, a long interval separated the initial increase in earthquakes and the eventual eruption, while in other instances, eruptions followed shortly after heightened seismicity.
Meanwhile, Alert Level 2, which signifies increased volcanic unrest, remains in effect over Mt. Kanlaon. Phivolcs cautioned that the heightened seismic activity raises the possibility of steam-driven or phreatic eruptions, as well as short-lived weak to moderately explosive eruptions at the summit. These could generate hazardous phenomena such as pyroclastic density currents, ballistic projectiles, ashfall, and rockfall.
Communities within the four-kilometer permanent danger zone (PDZ) were reminded to strictly remain evacuated, while those within a six-kilometer radius from the summit were urged to stay vigilant and ready for possible escalation of unrest. Authorities also advised increased alertness against potential lahar flows and sediment-laden streamflows, especially during periods of heavy rainfall.
Civil aviation authorities were likewise advised to keep aircraft away from the volcano’s summit area, as ash from sudden eruptions could pose serious risks to flights./PN
