Volcanologist Alex Baloloy said a seismic sensor has been set up at the monitoring station in Barangay San Benon in Irosin, Sorsogon.
The temblor, felt stronger in Irosin and Sorsogon City, originated from the fault off Sorsogon Bay and had a depth of one kilometer.
Baloloy, however, said, "There is still no volcanic activity to speak of."
People living near Bulusan fear that the volcano might erupt after successive aftershocks were felt after the earthquake.
Bulusan ejected ash in late 1995. It is one of three active volcanoes in Bicol; the two others are Mayon in Albay, and Mt. Iriga in Camarines Sur. — Celso Amo