Manila, April 22 -- 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 s...