Magnitude 7.2 Cebu earthquake: Is Metro Manila prepared for the next one?

Just when you think the Philippines can’t get any further “tests” from the “Almighty” on account of the appalling pork barrel thievery, chronic flooding, and yesterday’s hijacking of its capital city by a religious group, yet another Act of God hits. This time it is in the form of an earthquake devastating the Queen City of the mid-south, Cebu, and nearby Bohol Island. Reports are trickling in about several casualties and the destruction of historic structures around those areas (notably Baclayon Church in Cebu Bohol, a UNESCO-listed Heritage Site). Four people were killed at the Pasil Fish Port in Cebu City after a a wall collapsed according to the Office of Civil Defense Region VII. Another two people had reportedly been killed after a roof at a public market collapsed.

Fault lines such as this one are disasters waiting to happen.
Fault lines such as this one are disasters waiting to happen.
Nature hadn’t dealt us very nice cards as far as seismic stability goes. The Philippines’ islands are situated smack between two major fault lines running along its eastern and western coasts. Metro Manila is particularly at risk of catastrophe if an earthquake of a magnitude similar to this one strikes.

The Valley Fault System known formerly as the Marikina Valley Fault System is a group of dextral strike-slip faults which extend from San Mateo, Rizal to Taguig City on the south; running through the cities of Makati, Marikina, Parañaque, Pasig and Taguig. The fault poses threat of a large-scale earthquake with a magnitude of 7 or higher within the Manila Metropolitan Area with death toll predicted to be as high as 35,000 and some 120,000 or higher injured and more than three million that may be in need of evacuation.

Reports coming from officials of the Philippine Institute of Volcanology and Seismology (Phivolcs) back in 2011 have indicated that these parts of Metro Manila may be in imminent danger as said fault is “ripe for another major movement”…

Phivolcs deputy administrator Bartolome Bautista earlier said the Marikina Valley fault moves every 200 and 400 years. The last major movement occurred 200 years ago.

The Luzon earthquake which occurred on July 16, 1990 produced a 125 km-long ground rupture that stretched from Dingalan, Aurora to Cuyapo, Nueva Ecija as a result of strike-slip movements along the Philippine Fault and the Digdig Fault within the Philippine Fault System. Infrastructure on top of the rupture was completely destroyed.

Collapsed 400-year-old churches may be the least of our problems in the long run.
Collapsed 400-year-old churches may be the least of our problems in the long run.

Even more disturbing is a report originally published in the Manila Standard Today on April 2012 (copy can be found here) of a study that revealed that Angat Dam in Bulacan, which requires urgent rehabilitation, sits on the same Western Marikina Valley Fault.

The experts said an earthquake on the Western Marikina Valley Fault could trigger movement on the fault lines beneath the dam and its dikes. If those were damaged, they warned, the flood wave would affect not only areas near the Angat River but extend both upstream and downstream into the floodplain of the Pampanga River.

That would flood 30 cities and towns in Bulacan, Pampanga and Metro Manila, they said.

The flood waters in some areas of Norzagaray, Bustos and Baliuag could reach as high as 30 meters during the initial break of the dam, the experts’ report says. They could reach as high as 10 meters in Pulilan and Plaridel and all the way to Calumpit and Malolos City. Areas of Pampanga and Metro Manila could experience floods of three to five meters, they said.

Ultimately awareness and management of disaster preparedness begins with those who are most potentially at risk when disaster strikes — the Filipino public. It isn’t enough to rely on heroics that emerge in the aftermath of a disaster. The sight of politicians personally distributing relief goods to victims in devastated areas is getting old. The biggest bang for buck lies in preventive and risk mitigation measures, and a key success factor underpinning such initiatives lies in having the right legislation in place to help guarantee that such measures are put in place and the right execution faculties in place to deliver those measures where they count.

[NB: Parts of this article were lifted from the article “Marikina Valley Fault System” in a manner compliant to the terms stipulated in the Creative Commons Attribution-ShareAlike 3.0 Unported License that governs usage of content made available in this site. Photo of Bohol church courtesy]