Phivolcs logs increased seismicity in Bulusan Volcano

FILE: Mount Bulusan view from Sorsogon City Coastal Road, Sorsogon City, Sorsogon. (Photo By Patrickroque01/Wikimedia Commons, CC BY-SA 4.0)

By Ma. Cristina Arayata, Philippine News Agency

MANILA – An increase in seismic activity was observed in Bulusan Volcano in Sorsogon province, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.

Ninety-four volcanic earthquakes were recorded since 3 a.m., the seismology agency said in an advisory late Monday.

Of the 94, majority or 90 were weak and shallow volcano-tectonic (VT) earthquakes produced by rock fracturing while four were low-frequency volcanic earthquakes produced by the movement of fluids.

Phivolcs said the volcanic earthquakes were generated within 20 km. deep beneath the Bulusan edifice, with nearly half being shallow events.

Meanwhile, the degassing activity at the summit crater and active vents has been very weak to moderate for the same period.

“The slight increase in volcanic earthquake activity could be caused by hydrothermal activity, which could lead to short-term pressurization of the edifice,” Phivolcs said.

Alert Level 0 (normal) is maintained over Bulusan Volcano but there are chances of steam-driven or phreatic eruptions from the crater and/or its active vents on the summit that could occur suddenly and without warning.

Local government units and the public are advised to refrain from venturing into the 4-km. radius permanent danger zone, particularly near the vents on the south-southeastern slopes, due to the possible threat of sudden volcanic hazards, such as rockfall, landslide, ballistic projectiles, small pyroclastic density currents and others.

Aviation authorities should also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft, Phivolcs said.