New fault named Bogo Bay Fault identified as quake source
Officials and scientists have confirmed that the recently named Bogo Bay Fault is the source of the magnitude-6.9 earthquake that jolted northern Cebu on September 30. A team from the Philippine Institute of Volcanology and Seismology (Phivolcs) announced on October 3 that the fault’s on-land extension lies in Sitio Looc, Barangay Nailon, Bogo City. The discovery helps explain the complex ground movements and widespread aftershocks that followed the initial tremor.
What was observed on the ground
Field verification revealed clear signs of fault displacement within a two-meter-wide deformation zone. Observers documented fault scarps, open cracks, and small pressure mounds, all consistent with a right-lateral fault movement. In initial measurements, surface rupture extended about 200 meters, while drone surveys indicated the rupture could stretch as far as 1.5 kilometers. Experts emphasize that these figures are preliminary and that ongoing field mapping is needed to determine the full extent of the fault.
Expect continued aftershocks
In the days following the quake, Phivolcs warned residents to brace for strong aftershocks and to secure homes and avoid unsafe structures. As of 8 p.m. on Friday, the agency logged 4,581 aftershocks, ranging from magnitude 1.0 to 5.1. About 883 aftershocks had been plotted or located, with 22 felt by people. Officials stressed that people should rely only on official advisories for safety instructions and evacuation information.
Destruction and ongoing relief work across Cebu
The impact of the earthquake extended beyond the immediate earthquake zone. The Cebu provincial government reported that infrastructure damage in the province’s fourth district alone had reached about P3 billion as of October 2. The tally covers roads, buildings, and ports damaged in Bogo City and the municipalities of Bantayan, Daanbantayan, Madridejos, Medellin, San Remigio, Santa Fe, Tabogon, and Tabuelan. Earlier figures had placed infrastructure damage at around P2 billion, a figure that did not yet include schools and hospitals.
DPWH Secretary Vince Dizon ordered urgent inspections of classrooms and healthcare facilities, emphasizing that schools must be ready for use as evacuation centers if needed. Patients at Cebu Provincial Hospital in Bogo City have already been relocated to other facilities as a precautionary measure. Dizon directed DPWH Central Visayas to mobilize contractors from Cebu and nearby provinces to accelerate rehabilitation work.
Relief and coordination
Relief operations continue in tandem with infrastructure assessments. Social Welfare Secretary Rex Gatchalian confirmed that food packs and other assistance have reached northern Cebu. Capitol Command Center head Resti Arnaiz assured residents that aid is being distributed across various towns, not only in Bogo City. He acknowledged delays in some districts and apologized to families awaiting support while coordination with local governments is finalized.
As investigators expand their field work to determine the full extent of the Bogo Bay Fault, residents are urged to stay informed through official channels. Preparedness, secure housing, and clear evacuation routes remain vital as aftershocks continue to shape recovery efforts in Cebu.
