Increased seismicity was observed in Kanlaon Volcano as it generated 64 volcano-tectonic (VT) from midnight on Thursday, the Philippine News Agency (PNA) reported citing the Philippine Institute of Volcanology and Seismology (Phivolcs).
In an advisory sent at 11 a.m., the Phivolcs said the VT earthquakes were of magnitudes 0.9 to 2.9 and were 2 to 8 kilometers deep.
"VT earthquakes occur around volcanoes when magma moves upward. As magma rises towards the surface, it puts stress on the surrounding rocks, producing earthquakes," Phivolcs Director Teresito Bacolcol told the Philippine News Agency. He explained that when VT earthquakes become more frequent than tectonic earthquakes, it indicates magma activity beneath the volcano.
Meanwhile, Kanlaon's volcanic sulfur dioxide gas emission averaged 7,087 tonnes on Wednesday.
The Phivolcs reminded the public that Alert Level 2 (increasing unrest) prevails over Kanlaon, but that current seismic activity may lead to eruptive unrest and an increase in the alert level.
Entry into the 4-kilometer-radius permanent danger zone is prohibited to minimize risks from volcanic hazards such as pyroclastic density currents, ballistic projectiles, rockfall, and others.
Communities living beside river systems on the southern and western slopes, especially those that have already experienced lahars and muddy streamflows, are likewise advised to take precautionary measures when heavy rainfall over the volcano has been forecast or has begun, Phivolcs said.
