Volcanic quakes raise eruption risk at Kanlaon

BACOLOD CITY — A total of 105 volcanic-tectonic (VT) earthquakes were recorded beneath Kanlaon Volcano from Thursday noon to Friday morning, prompting the Philippine Institute of Volcanology and Seismology (Phivolcs) to warn of possible eruption.

According to Mari-Andylene Quintia, Phivolcs resident volcanologist, the strongest was a magnitude 3 volcanic earthquake recorded at 2:10 a.m. on Friday.

Phivolcs recorded 94 volcanic earthquakes from midnight to 11:59 p.m. on Thursday. The quakes ranged from magnitude 0.9 to 1.8 and occurred at depths of 0 to 11 kilometers beneath the volcano’s western flanks.

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READ: Kanlaon Volcano in Negros emits ash on Thursday morning (Aug. 13)

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VT earthquakes are generated by rock fracturing. Phivolcs said the increase in VT activity strongly indicates progressive rock fracturing beneath Kanlaon as rising magma or magmatic gas forces its way toward the surface.

A sustained and voluminous degassing plume from the summit crater was also observed on Thursday.

Phivolcs said the combination of increased VT activity and intensified degassing indicated that significant volcanic gas at depth may be forcing its way upward, triggering earthquake activity and increased plume activity at the summit crater.

Alert level 2 remains in effect over Kanlaon, indicating that the volcano is experiencing increased unrest.

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Phivolcs warned that the heightened VT activity and voluminous degassing could increase the possibility of steam-driven or phreatic eruptions, as well as short-lived weak to moderately explosive eruptions at the summit.

Hazards

Such eruptions could generate life-threatening hazards, including pyroclastic density currents, ballistic projectiles, ashfall and rockfall.

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Communities within the 4-km permanent danger zone were advised to remain evacuated, while those within 6 km of the summit crater were urged to remain vigilant and prepared for possible worsening unrest.

Phivolcs also warned of possible syn-eruptive lahars and sediment-laden streamflows in channels draining the volcano if heavy rains occur during periods of eruptive unrest.

Civil aviation authorities were advised to warn pilots against flying near the summit because ash from a sudden eruption could pose a hazard to aircraft.

Phivolcs said it continues to closely monitor Kanlaon and will immediately communicate significant developments concerned stakeholders.

Quintia said Kanlaon has recorded four weak eruptions so far this year—on Feb. 19, Feb. 26, March 15 and July 9.

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The eruptions prompted authorities to maintain heightened monitoring of the volcano and impose safety measures around its permanent danger zone.