Newly-identified fault in Bogo City triggered 6.9-magnitude earthquake

The Philippine Institute of Volcanology and Seismology (Phivolcs) has traced the source of the Sept. 30 magnitude 6.9 offshore northern Cebu earthquake to a newly-identified fault in Bogo City, Cebu.

- By ELLALYN DE VERA-RUIZ and JEL SANTOS

Phivolcs on Friday, Oct. 3 said its Quick Response Team "identified the onland extension of the fault that generated the Sept. 30 earthquake" in Sitio Looc, Barangay Nailon.

The agency has since named the feature the "Bogo Bay Fault."

Phivolcs explained that the Bogo Bay Fault is the onland extension of the offshore fault initially identified as the generator of the Cebu earthquake.

Since the feature had not been mapped before, it is now considered a newly-identified fault.

The experts found evidence of the rupture, which included "open cracks, local pressure mounds, and fault scarps within a two-meter-wide deformation zone." According to Phivolcs, "initial ground mapping measured about 200 meters of rupture, but a drone survey imaged approximately 1.5 kilometers of fault-related features, indicating ment." right-lateral moveIt added that "field verification is ongoing to determine the full extent of the rupture zone."

Aftershocks

Meanwhile, seismic activity has persisted in Cebu and nearby areas.

As of 12 p.m. on Saturday, Oct. 4, Phivolcs said a total of 5,228 aftershocks have been recorded by its monitoring instruments. Of these, 1,023 have been plotted, while 22 were reported felt by communities.

The agency said the strongest aftershock so far registered magnitude 5.1, while most were small tremors ranging from magnitude 1.0 to 3.0.