With the series of strong earthquakes that hit parts of Mindanao this year, there is increasing worry about the safety of structures in quake-hit areas.

Officials of the Philippine Institute of Volcanology and Seismology (Phivolcs) have urged residents to have their houses checked by engineers because of the multiple major earthquakes that happened in the Cotabato and Davao area starting October this year.

• READ: Phivolcs to quake survivors: Get your houses checked by engineers

Engr. Rex Sirilan, head of research and development of structural engineering firm Sy Squared, said there has even been talk among engineers on whether there is a need to amend the National Building Code of the Philippines or Republic Act no. 6541.

“We haven’t encountered such strong (earthquakes),” he told ABS-CBN in a phone interview. He said that while the building code is at par with international standards, it would have been better if engineers on the ground had enough time to check the buildings and make sure they were retrofitted if it was necessary.

The first major earthquake (magnitude 6.3) hit Cotabato on October 16. It was followed by magnitude 6.6 and 6.1 on October 29 and a magnitude 6.5 quake on October 31. The most recent major temblor was a 6.9-magnitude earthquake that struck Davao del Sur on December 15.

• READ: 'Blind faults'? Phivolcs explains series of strong quakes in Mindanao

Sirilan said that because of the “unique case of Mindanao,” there might be a need to update the building code.

But for Engr. Cesar Pabalan, former head of the Association of Structural Engineers of the Philippines (ASEP) and of the Philippine Institute of Civil Engineers (PICE), the specification in the Building Code and the National Structural Code of the Philippines should suffice.

He said the only thing they want amended are the requirements under the two codes to make building processes more efficient.

“The design, as far as the Building Code is concerned, (should be able to) withstand those several earthquakes without collapse,” said Pabalan, who is currently ASEP’s disaster mitigation, preparedness, and response head. “Even if earthquakes happen one after the other. There should be no collapse.”

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Pabalan, who went to Mindanao after the October quakes, said most of the buildings they checked were structurally sound. Only a few collapsed and those had “irregularities” that should have been addressed.

He said that while there might be damage, structures that strictly followed the building code should not collapse.

“If it collapses, then there is something wrong with the building,” Pabalan said.

He said, even buildings constructed decades ago should also not collapse since they should have been made to comply with the Building Code.

One problem, he said, is that houses and other one-storey buildings are sometimes constructed without an overseeing engineer.

“Those are usually damaged because they are not engineered structures. And because of the use of materials,” he said, adding that the hollow blocks used might be of inferior quality.

Pabalan said one useful resource that homeowners can check is Phivolcs' guidelines on how to ensure that a house is safe from an earthquake.

The “How safe is my house?” flyer includes questions such as whether if a house has 6-inch external walls.