Kanlaon tremors rise, Negrenses urged to stay alert

By Glazyl M. Jopson

BACOLOD CITY — The Office of Civil Defense–Negros Island Region (OCD-NIR) has reiterated its call for vigilance following a rise in volcanic-tectonic earthquakes at Kanlaon Volcano, as reported by the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

According to a PHIVOLCS advisory issued Sunday morning, a total of 41 volcanic-tectonic earthquakes were recorded by the Kanlaon Volcano Network between 11 p.m. on Sept. 13 and 10 a.m. on Sept. 14.

“As reported by PHIVOLCS, dumami ang earthquakes from last night until Sunday morning, that means hindi pa puwedeng magrelax,” said OCD-NIR Director Donato Sermeno in a phone interview on Sunday.

PHIVOLCS stated that the earthquakes ranged from magnitude ML 0.8 to ML 4.6 and were generated at depths of 0 to 7 kilometers beneath the northwestern flanks of the volcano.

The strongest of these tremors was felt at Intensity III in La Carlota City, Bacolod City, and Canlaon City, as well as in Bago City, Murcia, and La Castellana in Negros Occidental, based on reports gathered through social media.

Sermeno confirmed that no damage has been reported, but warned that the threat of eruption remains present.

He said this activity underscores the need for continued alertness, especially since Kanlaon remains under Alert Level 2.

Sermeno added that local disaster risk reduction and management teams have been instructed to closely monitor both the volcano’s behavior and their respective areas.

When asked about the possibility of relocating residents within the six-kilometer danger zone if activity continues, Sermeno acknowledged the logistical challenges, citing past evacuations that lasted up to seven months.

However, he said such a measure is still possible, especially if the alert level is raised again.

PHIVOLCS explained that the recent tremors were caused by rock fracturing beneath the volcano, which indicates rising magma or magmatic gas moving toward the surface.

Volcanic sulfur dioxide (SO₂) emissions from Kanlaon’s summit crater averaged 1,122 tonnes per day on Sept. 13, which is lower than the medium-term average of 2,594 tonnes per day recorded since Jan. 1, 2025.

These readings suggest that the blockage of volcanic gas emission—also known as closed-system degassing—may lead to pressurization and edifice swelling, increasing the risk of a moderately explosive eruption.

Kanlaon previously erupted on June 3 and Dec. 9, 2024, significantly affecting La Castellana, La Carlota, and parts of Moises Padilla and Bago City in Negros Occidental, as well as Canlaon City in Negros Oriental.

In July, PHIVOLCS lowered Kanlaon’s alert status from Level 3 to Level 2, allowing over 3,000 evacuees to return to their homes in affected areas.

Despite the downgrade, PHIVOLCS reminded the public that Alert Level 2 indicates increased unrest and a higher likelihood of sudden, steam-driven or phreatic eruptions.

It warned that such eruptions could result in hazardous events like pyroclastic density currents (PDCs), ballistic projectiles, ashfall, and rockfalls.

PHIVOLCS urged residents within the four-kilometer Permanent Danger Zone to remain evacuated and advised those within the six-kilometer extended danger zone to stay alert.

It also warned of potential syn-eruption lahars and sediment-laden streamflows in channels around the volcano, particularly during intense rainfall events.