The Philippine Institute of Volcanology and Seismology (Phivolcs) has so far recorded 123 aftershocks following the magnitude 6.0 earthquake that struck Batuan, Masbate around 2:10 a.m. on Thursday, Feb. 16.

As of 12 p.m., Phivolcs had detected 123 aftershocks, with magnitudes ranging from 1.5 to 4.2.

Of the recorded earthquakes, 44 earthquakes have been plotted by three or more stations, while 13 tremors were felt.

The epicenter of the 6.0-magnitude earthquake was traced 11 kilometers southwest of Batuan, Masbate, at an estimated depth of 10 kilometers.

According to Phivolcs, the 6.0-magnitude quake, or “mainshock,” was preceded by a 5.0-magnitude quake, or “foreshock” on Feb. 15.

Foreshocks are earthquakes that precede larger earthquakes (mainshock) in the same location.

“After this will be aftershocks unless there will be an earthquake higher than the mainshock on the same fault. In seismology, we call this sequence of events as foreshocks, mainshock, and aftershocks,” Phivolcs said.

It pointed out that the magnitudes 5.0 and 6.0 earthquakes were generated by the movement along the Philippine Fault-Masbate Segment that has been the source of large earthquakes—the most recent in 2020 (6.6-magnitude) and 2003 (6.2-magnitude).