Earlier last October, a 7.2-magnitude earthquake shook Bohol and Cebu. According to the National Disaster Risk Reduction Management Council (NDRRMC), it killed around 200 people and injured close to a thousand. The damage cost is estimated at around P2.257 billion in infrastructure, the NDRRMC added.
Meanwhile, seismologists are anticipating an earthquake of the same magnitude (or higher) to hit Manila in the near future.
On October 17, the International Day for Disaster Risk Reduction, Philippine Institute of Volcanology and Seismology (PHIVOLCS) Director Renato Solidum Jr. presented a three-year study conducted by the Australian and Philippine governments. It revealed the last destructive earthquake to hit Manila was on August 20, 1658, measured at magnitude 7.5.
The cause of the 1658 earthquake was the Marikina Valley Fault System. A complex fault system stretching from northeast of Manila and traversing Marikina; Pasig going to Muntinlupa, the fault system threatens to generate large-scale earthquakes within Metro Manila.
A 2004 Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS) reveals that the last significant earthquake recorded was in 1658 — 355 years ago. The Marikina Valley Fault system is said to generate one major earthquake every 400 years.
During a Senate inquiry regarding the country’s disaster preparedness a day after the Visayan quake, PHIVOLCS Deputy director Bartolome Bautista explained that though an earthquake is likely, “Hindi lang natin masabi ang exact date and time [We cannot tell the exact date and time].”
Fire and building damage maps are based on a very specific disaster simulation from MMIERS. Model 08: 7.2 slip strike earthquake originating from the West Valley Fault.
A plausible scenario
MMEIRS hypothesizes that if a 7.2 magnitude earthquake from the Marikina Fault System hits Metro Manila, the tremor would reach a maximum magnitude of XIII within Metro Manila. The PHIVOLCS Earthquake Intensity Scale designates the number as “very destructive”.
In addition, a high magnitude earthquake originating from Manila Bay poses a huge tsunami hazard to Manila.
A separate study conducted by the Australian Agency for International Development estimates that a strong earthquake has the capacity to kill at least 37,000 persons and injure at least 604,000 others, with 16,000 severely hurt.
MMEIRS warns that the potential for severe building damage and fire spread is high and will be concentrated in Metro Manila, as well as the East National Capital Region (NCR), according to hazard maps. It also forecasts that the severe extent of infrastructural damage would isolate East and West NCR from one another.
MMEIRS and PHIVOLCS indicated high liquefaction risks in Manila, Pasay, Taguig and Pateros. Liquefaction is a phenomenon where the strength and stability of the land is reduced due to water saturation, often induced by high magnitude earthquakes. Liquefied soil has a reduced ability to support heavy weights: structures.
According to Malate Building Inspector Engr. Angelito Quiñones, most buildings in DLSU’s vicinity are recent constructions held to higher standards and better engineering techniques. Based off US standards, he estimates that these structures could stand up to a short magnitude 8 earthquake. “Pag humaba yan, mga 30 seconds, may problema na tayo dyan [Should the earthquake take a while, around 30 seconds, it won’t be a good thing],” he says, referring to the high possibility of a building collapse during a long earthquake, like the one in Bohol.
A few kilometers away from Manila Bay, DLSU is situated in Malate, where infrastructures are built on soft soil. This makes its land prone to liquefaction when disturbed by great seismic activity.
To counter this risk, Quiñones explains that newer buildings are usually anchored by piledriving. Steel foundational poles are driven deep into hard soil, reducing the risk of building collapse. Quiñones elaborates that engineers are also required by the government to test soil conditions and adjust building materials to fit the construction project.
Furthermore, the DLSU campus intersperses with high-rise condominiums and construction projects from varied real estate developers. Regarding apprehensions about high rises in the area, City Hall’s DLSU Inspector Engr. Romero Estipona mentions that high rises are less prone to “pancake collapse”. Instead, medium rise buildings are at greater risk for this.
Quiñones assures that construction projects approved by the Manila government have been precalculated to maintain its integrity in the construction process.
Estipona assesses that buildings within the DLSU campus have no indication of being structurally weak. He explains that most of his team’s recent observations were topical issues, e.g. cracks, which get patched by DLSU’s maintenance teams regularly.
Civil Engineer and Environmental Planner Dr. Angel Lazaro III warns that determining whether a building is truly structurally safe involves more than annual inspection. Such assessments require a detailed capacity and demand analysis on each member of the building — i.e. its beams, columns, etc. — as well as numerous simulation tests.
Though conceptually simple, Lazaro explains that these assessments are tedious. The cost of such initiatives often reach into the millions: each unit has to undergo a thorough capacity analysis, then factor in additional demands (attached structures like windows, active weight, earthquakes) on the individual units.
He says that institutional buildings like DLSU are more accountable to the public and could source more funds, giving them an incentive to undergo these strict building assessments and take the necessary actions to strengthen their structures.
In contrast, Lazaro emphasizes that many companies, especially those that own commercial and residential buildings, have little to no incentive to regularly assess the structural integrity of their buildings.
He adds that the government currently do not require such assessments or reviews, either. Decisions like who to subcontract or hire, or when to conduct a review, relied on the owner’s discretion.
Lazaro’s firm, Angel Lazaro and Associates International, were also the ones involved in the retrofitting design of St. La Salle Hall, which was retrofitted with carbon fibers a couple of years ago to stand up to major disasters.
As part of Disaster Risk Reduction, DLSU’s community engagement arm, the Center for Social Concern and Action (COSCA), has conducted multiple disaster risk management training programs for primary responders within DLSU.
COSCA Program Manager and Community Engagement Coordinator Joseph Rosal stresses the immediate need for the Lasallian community to be more aware of the risks and geohazards that surround their home and the schools/workplaces they attend on a daily basis.
Asserts Rosal, “Magandang nalalaman ng bawat isa kung anong gagawin when the disaster happens… we get a disaster protocol going: people would go to a specific area for this specific case. Next day, we all go to school… rather than we count casualties. We have information given by the government. It’s there! So what is La Salle doing about this?” he asks.
According to Security and Safety Office (SSO) Director Dionisio Escarez, there are designated evacuation places per area within the campus. He acknowledges the likelihood of falling debris and damage, and is currently designing emergency routes and a risk reduction protocol to guide survivors to safety once outside the campus.
He mentions that the SSO is still strategizing on how to further evacuate affected groups to the Rizal Park in Roxas Boulevard, the 58 hectare historical park 4 kilometers away — and the only large open space nearby.
He points out there are emergency maps and safety information posted within campus. Escarez mentions that the SSO wants to tap student channels like the University Student Government to disseminate information.
Escarez assures that there are trained marshals and disaster response teams to guide the Lasallian community to safety.
In addition, DLSU conducts fire drills twice a year, and earthquake drills once a year.
Lazaro acknowledges the grim prospect of a post-earthquake Metro Manila, especially in the context of Manila’s poor urban and environmental planning.
On improving upon the infrastructural conditions of structures in the city, he says, “What you do here is you try to minimize [the damages] if you can… There must be a system to prioritize. You prioritize hospitals, you prioritize the law enforcement. Yung nangyari sa Tacloban – mismong police ang nabagyo, therefore wala nang nagbabantay [What happened in Tacloban was that the police were the ones affected, so nobody was there to handle things].”
He adds, “The next thing, you make sure that the schools are safe. Make sure that the malls are safe [because that’s where a lot of people are]. Call them – for a lack of a better term – critical structures.”
Lazaro laments that there is no standardized system or guidelines mandated by the government, leaving designers and engineers on their own. He recommends a peer review system for private structures, especially.
Granted the dangerous reality of Manila, the City Hall’s Annual Building Inspector Head Engr. Rommel Dimitui stresses vigilance: awareness, alertness, preparedness, and prayers.
Infographics by Denver Banlasan & Cheska Martin, implemented by Jelvin Base & Jan Lim