Phivolcs warns of magnitude 7.2 to 7.5 quake in Cebu: “Potentially active fault”

CEBU, Philippines — Following the magnitude 7.8 earthquake that jolted Mindanao on Monday, June 8, the Department of Science and Technology–Philippine Institute of Volcanology and Seismology (DOST-PHIVOLCS) warned about a “potentially active fault” in Cebu that could generate a magnitude 7.2 to 7.5 earthquake if triggered.

During a news forum yesterday, June 9, Engr. Robinson Jorgio, director of the DOST-PHIVOLCS Visayas Cluster Monitoring Center for Earthquake and Tsunami, addressed concerns about whether the recent Mindanao earthquake and its continuing aftershocks could affect the Visayas region because of its proximity.

Jorgio explained that the earthquake in the southern Philippines came from the Cotabato Trench, which is located far from the fault systems in the Visayas, particularly those in Cebu. As such, he said it is unlikely to affect the region's fault systems and trenches.

"They are different," he said.

While discussing the distinction between earthquake magnitude and intensity, Jorgio noted that Cebu has a potentially active fault line known as the Central Cebu Fault System (CCFS).

Located near Cebu City, the fault could generate a magnitude 7.2 to 7.5 earthquake if triggered, raising concerns about the possibility of "The Big One."

"Pag sinabing potentially active, ibig sabihin 5,000 years walay activity," he said.

Jorgio added that monitoring efforts for the possible occurrence of "The Big One" are ongoing.

PHIVOLCS continues to coordinate with various local government units (LGUs) to assess potential scenarios should a magnitude 7.2 to 7.5 earthquake strike Cebu.

"If we're going to simulate the possible intensity across Cebu, it could reach Intensity 8," Jorgio said.

He encouraged the public to remain prepared to help minimize potential damage and casualties.

"Zero casualty atong target man," he added.

Jorgio also said there could be possible warning signs months before a major earthquake occurs, including earthquake swarms, which are clusters of small tremors that may precede a stronger event or the "main shake."

He further noted that all fault systems in the Visayas are being monitored as part of disaster preparedness efforts. However, he acknowledged that PHIVOLCS cannot monitor all faults simultaneously due to limited equipment, including accelerometers, seismographs, and ground-based GPS instruments.

Despite this, it was further clarified that Cebu is not experiencing an earthquake swarm.

An earthquake swarm, as explained, refers to a series of small to moderate earthquakes that occur in a specific area over a period of days, weeks, or even months.

He explained that the persistent seismic activity being recorded in Bogo City consists of aftershocks from the magnitude 6.9 earthquake that struck northern Cebu last year. He added that even minor tremors recently recorded in Lapu-Lapu City do not indicate an earthquake swarm in Cebu and should not be considered a sign of unusual seismic activity in the province.

Alcover calls out city’s preparedness

In Cebu City, Councilor Pastor M. Alcover Jr., in a privilege speech, called upon the government to strengthen its disaster preparedness efforts.

Citing data from PHIVOLCS, Alcover stressed the urgency of the matter, indicating that Cebu City is part of the CCFS.

“According to NDRRMC, naa ba tay plano sa response, recovery unya and rehabilitation kung mahitabo nga dunay dako nga linog sa syudad sa Cebu?” Alcover said.

“Sa ako rabang nabasahan sa PHIVOLCS, murag halos taga adlaw naay linog, although gagmay ra kaayo ang intensity, when in fact, last June 5 dunay linog sa Albay, so mao ning dakong pangutana karon, preparado ba ta?” he further asked.

Following the discovery of the Bogo Bay Fault in Bogo City, Cebu, by PHIVOLCS on October 3, 2025, the public was advised to avoid constructing buildings on top of or within 5 meters of either side of the fault.

The councilor cited that the deadly earthquake that occurred in Bogo City on September 30, 2025, with a magnitude of 6.9, claimed lives because of “unpreparedness.”

“Mao sad ni nahibato sa Bogo, nga wala sad naka andam ang Bogo, daghan-daghan sad ang kinabuhi na kalas,” Alcover said.

He pointed out that before any building, commercial establishment, office, condominium, school, hospital, or other structure is allowed to operate and accommodate occupants, there must be a thorough and uncompromising assessment of its structural integrity and compliance with the National Building Code and all applicable safety regulations.

“We cannot afford to wait for a catastrophic earthquake to expose weaknesses in our emergency response system,” Alcover said.

Alcover then requested the Cebu City Disaster Risk Reduction and Management Office (CCDRRMO), the Cebu City Rescue Unit, and all other concerned emergency response agencies, through the office of the city mayor, to submit a comprehensive earthquake preparedness and emergency response capability report.

He also requested an inventory and operational status report of rescue vehicles, emergency tools, disaster response assets, and available manpower.

“May gyud unta na taga barangay ma train tingali nga pag responde, onsay himuon during earthquake,” Alcover said.

Alcover also emphasized the need to assess the status of the emergency communication system, command center, and interagency coordination mechanisms to ensure they are fully equipped during disasters.

He raised concerns about existing deficiencies, operational gaps, and logistical challenges, along with recommendations necessary to enhance the city's disaster preparedness.

Alcover requested the Office of the Building Official (OBO), through the office of the city mayor, to submit a report on the implementation and enforcement of structural safety inspections.

He also discussed measures aimed at ensuring that commercial, residential, institutional, industrial, and public buildings within Cebu City are structurally sound and earthquake-resilient.

“Lives are lost not only because of the earthquake itself but also because of inadequate preparation and delayed emergency response,” Alcover said.

All resolutions raised were then approved by the City Council.

DOE: Visayas and Mindanao power grids still normal

The Department of Energy (DOE), on the other hand, is closely monitoring the possible impact of Mindanao power plant outages on the Visayas grid, particularly amid the current Yellow Alert status being observed in the region.

Mario C. Marasigan, DOE Supervising Undersecretary for the Electric Power Industry Management Bureau (DOE-EPIMB), explained during a virtual press conference yesterday that around 450 megawatts of power is typically exported from Mindanao to Cebu, forming part of the interconnection support between the two grids.

However, he clarified that the actual transferred capacity varies and is not always at the full 450-megawatt level.

At present, the DOE said both Mindanao and the Visayas continue to operate under normal market conditions, with sufficient available capacity still being shared between the grids despite ongoing outages in Mindanao.

Marasigan noted that since Mindanao has not yet reached peak demand due to several affected power plants, enough capacity remains to support interregional transfers for the time being.

He said the full impact on the Visayas grid will depend on how quickly affected plants in Mindanao are restored and whether the remaining outages will constrain available export capacity in the coming days.

He added that monitoring is being conducted on a daily and even hourly basis, particularly in coordination with the National Grid Corporation of the Philippines (NGCP), to determine whether any adjustments in power flows will be needed in the coming days.

The DOE emphasized that while there is potential for effects on Visayas supply conditions, the system remains stable at present, with adequate reserves still available to manage demand.

Marasigan said that the situation is being closely monitored due to the interconnection and power transfers between the two grids, particularly through electricity exports from Mindanao to Cebu.

He said that the full restoration of Mindanao’s generation capacity will determine the eventual impact on the Visayas grid. Once Mindanao reaches 100 percent restoration, its effect on inter-grid transfers will become clearer.

For now, based on projections from the NGCP and system outlook assessments, Mindanao’s demand remains lower due to ongoing outages, which allows some capacity to be shared with the Visayas.

Several power generation facilities in Mindanao experienced temporary outages following the magnitude 7.8 earthquake that struck Sarangani, with authorities confirming that the disruptions were due to automatic tripping mechanisms implemented for the safety and security of power infrastructure.

The DOE said that a total of 835 megawatts (MW) of capacity was taken offline at the height of the incident.

Marasigan further emphasized that despite the temporary capacity loss, there was no significant impact on the electricity market and that the remaining available generation capacity was sufficient to meet demand and maintain ancillary services.

Cebuano olympians in Gensan safe from quake

Meanwhile, Cebuano Olympians Ramon Solis and Elreen Ann Ando, together with 25 other delegates from Cebu, are confirmed safe in General Santos City after the magnitude 7.8 earthquake that struck off Sarangani, Mindanao.

Solis, who competed in the 1988 Seoul Olympics and now serves as one of the long-time national coaches of the Philippine weightlifting team, told THE FREEMAN that the tremor hit while the delegation was having breakfast, sending athletes and coaches rushing out of their hotel amid strong aftershocks.

Fourteen-year-old Jea Mae Palagtiw of the University of Cebu sustained a cut on her ankle from shattered glass at the hotel’s main door but has since been treated.

Palagtiw, rattled by the quake, rushed barefoot down the stairs during the evacuation.

“We were told to vacate the hotel for inspection but were brought back at night after building inspectors deemed it safe to return,” Solis said.

He noted that while the athletes are physically unharmed, many are somewhat drained and unable to rest well due to the continuous aftershocks.

Another Olympian coach, Christopher Bureros, confirmed that Cebu’s delegation totals 27 members, composed of three national coaches, nine national athletes, including Ando, three parents, and non-athlete companions.

He said their hotel continues to run on generator power due to the blackout in General Santos City.

“Na cancel na amo competition kay dili na safe ang situation sa mga building ug school,” Bureros explained. He added that aftershocks are still being felt in the city, keeping athletes uneasy.

Ando, who represented the Philippines in the Tokyo 2020 and Paris 2024 Olympics and was recently named SAC-SMC Athlete of the Year, was scheduled to compete yesterday, June 9, but was unable to do so after organizers declared the venue unsafe.

The powerful tremor forced organizers to call off the National Open Weightlifting Championships, where the Cebuanos had already secured multiple gold medals before the cancellation.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported the June 8 earthquake at magnitude 7.8. It was tectonic in origin, with its epicenter located off Sarangani Bay.

The tremor was felt strongly in General Santos City, Davao Occidental, Sultan Kudarat, and South Cotabato.

Tsunami warnings were briefly issued for coastal communities, and aftershocks persisted throughout the day.

Authorities confirmed casualties and widespread structural damage, including collapsed buildings and power outages.

As of yesterday, the Cebuano weightlifting team was safe in General Santos City, though its scheduled flight back to Cebu was cancelled. — Sofhia Grace Neri Marjorey B. Cantilla Meriane Katherine T. Espina CNU Interns (FREEMAN)