The country’s largest city, with an estimated 15 million inhabitants, Manila is sprawled across the West Valley fault, which seismologists say shifts every 400 to 600 years and most recently in 1658.
“If the lower range (estimate) is followed, then the fault is ripe to move,” said Bartolome Bautista, deputy director of the Philippine Institute of Volcanology and Seismology (PHIVOLCS).
According to two studies carried out by PHIVOLCS, greater Manila could be hit by a 7.2-magnitude earthquake that would reduce much of the city to rubble, kill at least 31,000 people, and injure about half a million more.
Preparing for such a disaster has taken on added urgency following the 25 April earthquake in Nepal that killed more than 8,000 people, and the 5 June quake in Malaysia’s Sabah state, which killed at least 18 people who were climbing Kota Kinabalu mountain.
Sabah deputy chief minister Joseph Pairin Kitingan told reporters that the tremor was caused by a photo session of tourists posing naked at the peak, which angered the spirits of the mountain.
Seismologists have a rather different explanation that involves shifts of tectonic plates beneath the earth’s crust.
They warn that the Philippines is at an even higher risk than neighbouring Malaysia, because the archipelago sits on the Rim of Fire, a string of volcanoes and sites of seismic activity that lines the Pacific Ocean and accounts for about 90 percent of the world’s earthquakes.
Increased preparedness
Since the Nepal earthquake, authorities in Manila have scaled up earthquake preparedness plans, including carrying out simulation drills in schools and hospitals.
The government has distributed to city leaders an atlas of maps showing in detail areas traversed by the fault system. A mobile "earthquake simulator" has been travelling to schools to show students what to expect during tremors. Seismologists are working with the city to fast-track the setting up of markers to indicate where the fault line lies underneath 84 communities.
“Are these enough? It is very hard to tell. I think we will only know if we have prepared enough after the big one,” said Bautista of PHIVOLCS.
Bautista drew parallels with the Nepalese capital Kathmandu, which also lies on a major fault that experts had warned was due to move.
“The Nepalese government had initiated preparedness activities, but at a much slower phase due to budgetary constraints,” he said. “One good lesson that we can learn from this event is that, preparedness should be given priority and that it should be done at a sustained and rapid phase.”
He pointed to the Philippines’ own experience with earthquakes, including the 7.2-magnitude quake that rocked the central Visayas region in October 2013, killing 200 people. Particularly hard hit was the island of Bohol and the city of Cebu.
The reason there were relatively few deaths was because of the low population and because most buildings were low-rise and made of wood and other light materials. However, the destruction would be far worse in Manila with its large population and urban sprawl, which includes informal settlements and concrete buildings that have not been built according to safety standards.
Experts estimate that 170,000 residential homes would be destroyed and 340,000 damaged, Bautista said. Bridges would also fall, water pipelines and electric cables would be cut and at least 95 kilometers of phone cables would be rendered useless.
“The metropolis might also be separated into north, south, west and east due to building collapse, (and) fire and road damages,” he warned. “As a result, there is a probability of isolation and difficulty in accessibility from one area to another which could potentially affect any plans for implementing rescue operations.”
Push for public awareness
Red Cross secretary general Gwendolyn Pang said the agency has been training its staff to respond to a major quake, but she also urged residents to take their own precautions.
“Everyone is advised to evaluate the safety of his own house and to consult an engineer if the building is found to be unsafe and is located in highly hazardous areas,” she said.
Senator Bam Aquino, who has filed a resolution seeking to assess the local government’s preparedness, said there was a need to prioritise communities to “mitigate and recover from the impact of a massive earthquake.”
"A significant factor in ensuring earthquake safety is ensuring the ability of houses, buildings and all public infrastructure to withstand earthquakes even with magnitudes of 8 to 10," Aquino said in a statement.
“We need to learn from incidents that happened in Nepal, Cebu and Bohol,” he said. “Let us not wait for many lives to be lost and houses to be destroyed.”