90 Kanlaon volcanic earthquakes recorded in just 21 hours

Phivolcs says most of the earthquakes 'were generated within a depth of 20 kilometers beneath the southeastern sector' of Kanlaon Volcano's edifice

MANILA, Philippines – There were 90 volcanic earthquakes recorded at Kanlaon Volcano in Negros Island from 3 pm on Tuesday, July 2, to 12 pm on Wednesday, July 3, or a 21-hour period.

This indicates “increased seismic activity,” said the Philippine Institute of Volcanology and Seismology (Phivolcs) in an advisory issued at 1:15 pm on Wednesday.

Phivolcs classified 85 of the volcanic earthquakes as “weak low-frequency events that indicate the movement of volcanic fluids,” while the remaining 5 are “volcano-tectonic events…produced by rock fracturing.”

“Most of these earthquakes were generated within a depth of 20 kilometers beneath the southeastern sector of the edifice,” added the agency.

Sulfur dioxide (SO2) emission from Kanlaon also reached 5,083 tons per day on Tuesday, “the second highest emission from the volcano recorded this year and the third since instrumental gas monitoring began.”

The highest SO2 emission for 2024, so far – and also since instrumental gas monitoring began – was recorded last Friday, June 28, at 5,397 tons per day.

Since Kanlaon’s June 3 eruption, SO2 emission “has been persistently elevated,” averaging 3,254 tons per day. When the volcano is not in a state of unrest, the typical emission is only less than 300 tons per day.

Phivolcs has also observed inflation or swelling of Kanlaon’s entire edifice since March 2022.

“The overall monitoring parameters indicate that magmatic processes beneath [the] volcano may be driving current unrest, causing increased volcanic earthquake activity, persistently high concentrations of volcanic gas emission, and swelling of the edifice,” the agency said.

Kanlaon remains under Alert Level 2, which was raised also on June 3, shortly after the volcano erupted. This means the unrest may lead to further explosive eruptions “or even precede [a] hazardous magmatic eruption.”

Phivolcs again advised the public not to enter the 4-kilometer-radius permanent danger zone surrounding Kanlaon “to minimize risks from volcanic hazards such as pyroclastic density currents, ballistic projectiles, rockfall, and others.” Ashfall and lahar flows remain possible as well.

Kanlaon, which straddles the provinces of Negros Occidental and Negros Oriental, is one of the Philippines’ two dozen active volcanoes. – Rappler.com