Following a series of temblors over the last three days, the West Valley Fault that passes through 42 barangays in Makati, Taguig, Marikina, Pasig, Muntinlupa and Quezon City could trigger a 7.2 magnitude earthquake, causing massive destruction in Metro Manila and killing 35,000 people in the first hour alone.
READ: Samar shocker: 6.5 quake
The Philippine Institute of Volcanology and Seismology warned that “a Big One” would likely cause 500 instantaneous fires as well in Metro Manila and parts of Bulacan, Rizal, Cavite and Laguna, through which the 100-kilometer West Valley Fault runs.
In such a scenario, 170,000 residential houses would collapse, fires would burn about 1,710 hectares of land and properties, and 18,000 more people would be killed by a secondary disaster.
The shorter 10-km. East Valley Fault would put Rodriguez and San Mateo towns in Rizal at risk as well.
Experts said the government must inspect and assess all old buildings and vital structures.
“Old buildings need to be examined more closely and undergo extensive testing to gauge their vulnerability,” said Ernesto de Castro, president of an engineering services company, ESCA Inc.
“They must be retrofitted based on the [Building] Code. I know the government is doing it right now.”
ESCA was responsible for the structural retrofitting and code upgrade of the old Meralco Building along Ortigas Avenue in Pasig City in 2011. The project covered a floor area of about 41,340 sqm for the main edifice and 16,420 sqm for the annex.
“What we did in Meralco was retrofitting based on the 7.2 magnitude earthquake. The structure can withstand the 7.2 strong quake. It can be damaged but it will not collapse,” De Castro said.
The organization was also involved in the retrofitting and rehabilitation of the Ayala Bridge in San Miguel, Manila and the construction of SM Mall of Asia in Pasay City.
Experts said heritage sites are the most vulnerable structures that will be destroyed by earthquakes given their age and the number of calamities they have withstood in the past.
Nine years ago, the Department of Public Works and Highways conducted a thorough inspection and evaluation of 366 public structures, including school buildings in Metro Manila to ensure they can withstand a major earthquake.
Of the 366 buildings, 60 were recommended for urgent detailed evaluation.
Being one of the oldest cities in the country, Manila is most vulnerable to the “Big One,” the Metro Manila Development Authority said.
In case of a 7.2 magnitude earthquake, the MMDA said most parts of Manila will either be destroyed by huge fires or swept away by hundred-meter tall tsunamis, causing a horrific number of deaths and massive destruction.
READ: 16 dead in Luzon tremor; rescuers step up search
The MMDA is citing the earthquake damage scenario contained in the 2004 Metro Manila Earthquake Impact Reduction Study conducted by the government with the help of the Japan International Cooperation Agency.
The study details the effects of a powerful quake as a result of the sudden movement of the West Valley Fault.
MMEIRS showed that Manila was among the cities in Metro Manila identified as vulnerable sites in case a nighttime 7.2 magnitude quake strikes with an estimate of 6,200 fatalities and 21,000 injured.
Based on MMEIRS, the other cities identified as vulnerable sites were Quezon City with an estimated 5,800 deaths and 19,400 injured, while Pasig City would suffer 3,400 deaths and 11,900 injured.
The data also showed that Quezon City would have the biggest number of damaged residential buildings with 26,900 damaged houses followed by Manila with 26,200, Pasig with 23,000, Muntinlupa, with 13,500 and Taguig with 11,600.
READ: Belmonte warns QC to prepare homes for more quakes
Makati City Mayor Abigail Binay on Wednesday urged city residents whose houses are built on top of the West Valley Fault to relocate and said the city government would provide financial assistance.
The city government has inspected and declared 95 buildings in the city safe for occupancy following the recent quake that hit Metro Manila and other parts of Luzon on Monday.
Those structures include all public elementary and secondary schools in the city, University of Makati, Ospital ng Makati, three City Hall buildings, and 46 private buildings.
Mayor Binay said a total of 113 buildings consisting of 67 government facilities and 46 private buildings have been inspected to date.
Of these, 18 health centers require further evaluation by city engineers, apart from the covered court in Barangay Sta. Cruz, which was found with some visible cracks.
No casualties were reported in Makati.
Binay earlier ordered the Office of the Building Official and the Department of Engineering and Public Works to take the lead in conducting inspections on private buildings and government facilities in the city, respectively.
A total of 18 inspection teams from the OBO, DEPW, MDRRMO, General Services Department, Makati Health Department, Bureau of Fire Protection and Department of Education-Makati have been formed and mobilized starting Tuesday.
Binay also called on building administrators to coordinate with the OBO to schedule an inspection of their buildings, which she said could be done jointly with their own team of experts.
In an interview on the ANC news channel, PHIVOLCS Director Renato Solidum said short buildings are likely to sustain greater damage than high-rise buildings.
He said there was no need to panic in a high-rise condominium as long as people understand the phenomenon of the quake and the behavior of the building.
Solidum said the government was preparing for the “Big One,” which could hit Metro Manila and nearby provinces any time due to movements of the West Valley Fault, which moves every 400 to 600 years.
The West Valley Fault traversing through six cities in Metro Manila and nearby provinces and recorded a major quake in 1648.
“When the fault is very near us, the vibration of the ground is very fast. If that is the case, then the shorter building will be swayed more than the tall building,” he said.
A magnitude 4.5 quake hit 374 kilometers southwest of Sarangani, Davao Occidental on Wednesday at 11:28 a.m. with a depth of 270 kms.
Another quake of magnitude 4.7 yesterday hit 63 kms northeast of Baganga, Davao Oriental, at a depth of 11 kms.
Local government units were ordered to inspect all buildings in their respective areas to ensure public safety in the wake of the recent strong earthquakes that rocked the country.
Department of the Interior and Local Government Secretary Eduardo M. Año urged all LGUs, through building officials, to conduct inspections, as well as to coordinate with local offices of the Bureau of Fire Protection to ensure proper compliance with the National Building Code of the Philippines and the Fire Code of the Philippines.
“Aside from being physically present in your respective LGUs during these times, all local chief executives are reminded to not be complacent in doing preemptive measures to ensure that all structures are safe for use,” Año said in a statement.
The NBCP says that a buildign is considered dangerous if any portion of it has been damaged by fire, earthquake, wind, flood or any other cause.
“We should not be complacent. If you see any portion of a building wracked, warped, buckled, or settled to such an extent that walls or other structural portions have materially less resistance to earthquake, you should immediately inform the building owners. There should be no compromise when it comes to public safety,” he said.
Año also directed DILG regional directors and provincial directors to make an assessment on the quick action, as well as readiness of all LGUs during and after the earthquakes.
“All DILG field offices must assess the effectiveness and the lapses of the recent earthquake drills conducted by LGUs,” he said. “Check if LGUs have immediately set up their tactical operation centers. Have the local chief executives convened their respective Local Disaster Risk Reduction and Management Councils [LDRRMCs]?” the DILG secretary said.
Año has also ordered the Philippine National Police and the BFP to assist in rescue and relief efforts in earthquake affected areas in Luzon and the Visayas, especially in areas near the epicenter of the earthquakes.
PNP chief Oscar Albayalde has directed the Police Regional Office 3 under Brig. Gen. Joel Napoleon Coronel to activate their Disaster Incident Management Task Group and immediately provide assistance to the Regional Disaster Risk Reduction and Management Council (RDRRMC) 3, LGUs, other government agencies, and civilian groups.
In Quezon City, an initial assessment showed that the different office buildings in the House of Representatives were safe and fit for occupancy.
The inspection team will conduct a continuing assessment of the House buildings to monitor and ensure their continuous structural safety, said House acting Secretary General Dante Roberto Maling.
Work in the Supreme Court and Department of Justice resumed on Wednesday following the 6.1 magnitude earthquake that hit Luzon on Monday.
The decades-old buildings of the Court and DOJ in Padre Faura Street, Manila were both declared structurally sound after an inspection Tuesday.
“The SC engineering team has completed an initial inspection of all the buildings in the SC compound. No major and structural damage had been found on any of the buildings,” the SC Public Information Office said in a statement.
“Nonetheless, the SC will coordinate with the DPWH [Department of Public Works and Highways] for a more thorough structural assessment of all its buildings,” it added.
Chief Justice Lucas Bersamin and Court Administrator Jose Midas Marquez inspected the SC buildings and found damaged ceilings in some rooms.
The DOJ buildings were also declared safe after inspection.
Justice Secretary Menardo Guevarra said there was no damage to the buildings or to any equipment.
Guevarra said there were only cracks found in the exterior plastering of the new buildings, which “may easily be patched and are not a cause for concern.”
Work in both SC and DOJ was suspended Tuesday as a safety measure following the strong earthquake. With Maricel V. Cruz, Rey E. Requejo, Rio N. Araja, and PNA
READ: Cabinet looking at the impact of earthquakes on domestic economy