Phivolcs: Prepare for ‘big one’

MANILA, Philippines—With the country long overdue for a strong earthquake, the Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday urged home and building owners to check their structures for soundness.

Phivolcs Director Renato Solidum Jr. presented a study that showed that masonry houses—those structures with no structural beams and columns usually built for low-income families—could withstand a powerful earthquake with minor damage only if they were constructed according to the building code.

“The lesson in all this is that Filipino homes are generally safe from earthquakes as long as they follow prescribed guidelines in our building code, including the use of construction materials that pass quality standards,” Solidum said.

No shortcuts

“There are no shortcuts to safety,” he added.

The February study, conducted at a shaking laboratory in Tsukuba, Japan, with help from Japan’s National Research Institute for Earth Science, showed how two masonry houses—both one-room structures but of different construction—would react to a strong earthquake.

One was made with standard 6-inch-thick hollow blocks with 10-millimeter steel bar reinforcements spaced properly. The second model only used 4-inch hollow blocks and 6-millimeter steel bars—below building code requirements.

When both structures were subjected to tremors measuring 6.9 in magnitude—the same strength that devastated Kobe, Japan, in 1995—the second model collapsed.

The first model remained upright but with minor damage.

The need for stronger houses was highlighted by the recent earthquakes in Japan and New Zealand.

Low-cost homes

Thursday’s quake near Honshu, Japan, registered at 7.3 magnitude. No damage was recorded, unlike last month’s earthquake in Christchurch, New Zealand. That 6.3-magnitude quake destroyed buildings and caused over 200 deaths.

The Department of Public Works and Highways (DPWH) also raised concerns about low cost houses.

DPWH chief engineer Wilfredo Lopez said these houses did not follow construction guidelines and were therefore more vulnerable to destruction in the event of a major earthquake.

Solidum, citing a Phivolcs study, said there were at least 1.3 million buildings in Metro Manila. Of that number, 38 percent were residential buildings that could sustain slight to heavy damage should a 7.2-magnitude earthquake emanate from the West Valley Fault in Marikina City.

Homeowners should check their houses for signs of structural weakness, Solidum said. Building owners should consult with engineers on how to improve their structures, he added.

“We must change the mindset of homeowners. We have to educate them,” the Phivolcs chief said.