• GILBERT P. BAYORAN
The surge in tremors at the Kanlaon Volcano continues, as the Philippine Institute of Volcanology and Seismology recorded 72 volcano-tectonic (VT) earthquakes, as of 8 a.m. of September 15.
The strongest VT earthquake was felt at Intensity 1 in La Carlota City, Negros Occidental, and Canlaon City, Negros Oriental, according to the PHIVOLCS advisory.
Ma. Antonia Bornas, PHIVOLCS Monitoring and Eruption Prediction Division chief, said the VT swarms are caused by rock fracturing beneath the volcano, which indicates an upward movement of magma or magmatic gas, with intrusion from a 15 kilometer depth to the surface.
As we always say, meron po tayong ini-expect na major eruption ng volcano (we expect a major eruption), but medyo mahaba po ang period of unrest (but the period of unrest may take long), it could take years bago mangyari yon (before it happens), Bornas said.
In an advisory, PHIVOLCS said the blockade of gas emission may result in pressurization and swelling of the edifice, potentially leading to a moderately explosive eruption.
Bornas recalled that while VT swarms also happened at Kanlaon Volcano in September last year, no eruption took place.
However, in October, ash emissions started, followed by an eruption on December 9, she added.
Bornas admitted that it is difficult to assess whether an eruption is imminent on Kanlaon Volcano.
Definitely, there is always a chance for a moderate size eruption, she added.
But if you look at what happened last year, the eruption did not follow immediately, Bornas said.
Should there be any activity, no human activity should be at the 4 kilometer-permanent danger zone.
Amid the VT quake swarm, Bornas said there is no advice yet on the evacuation of those residing within the 6 kilometer extended danger zone.
Bornas also clarified that the earthquakes experienced by some local government units in central Negros in the past two days have nothing to do with the Kanlaon restiveness, as they were tectonic in origin.
Alert Level 2 remains in effect over Kanlaon Volcano.*
