WILL DAVAO CITY SURVIVE...

Will Davao City survive a “Bohol-type” tremor? MGB: Obey Building Code (edgedavao october 23, 2013)

WEDNESDAY, 23 OCTOBER 2013 02:35

Should a 7.2 magnitude Bohol type quake, which claimed 186 lives, happen in Davao City, the extent of destruction would depend on the readiness of private and public structures to follow the building code, according to the Mines and Geosciences Bureau (MGB) 11.

MGB supervising science research specialist Engr. Noel Angeles told Edge Davao yesterday that the new high rise buildings here followed the building code and will most likely survive the quake.

He said, however, “if there were mischiefs done during construction, like the contractor taking the materials to squeeze some money out of it, or speeding up the construction thereby neglecting important details in the process,” then the rate of survival will definitely decrease. 

The building code mandates that high rise buildings should have rollers in their foundation, to accommodate seismic waves from an earthquake, which makes the structure sway instead of it crumbling down. 

There are two major active fault lines in Mindanao, The Philippine Fault and the Mindanao Central Fault. While Bohol’s earthquake rocked the island in an up and down manner, these two faults produce earthquakes in a lateral manner. The Philippine Fault line lies along Davao Oriental, Compostela Valley, parts of Davao del Norte, Agusan and Surigao, while Central Mindanao lies along Cotabato region and Bukidnon. 

The kind of soil is another important factor in determining the damage an earthquake can inflict. In Davao City, majority of its soil are considered soft sediments, some portion from Mt Apo to Marilog district are hard volcanic soil.

Most of the soft sediment soil is found in the downtown area, which means, the city, especially the plainer area along the shorelines, will feel the strong effect of the seismic waves from an earthquake produced by the Philippine fault.

The soft sediment soil is evident when a person stays at the top floors of high rise buildings and as he or she would feel the vibrations of a moving truck passing by buildings such as The Marco Polo Dava, LandCo, Pryce Tower, and others, said Angeles. 

Another important issue that troubles most Dabawenyos is, will Davao City submerge underwater should strong earthquakes happen due to its soft soil?

According to Angeles, this is least likely to happen since compaction, the compression of consolidated materials to fill up the void spaces between sediments, will only be maximized should a strong quake happen. Compaction on sediments takes only .5 millimeter per anum, but can be maximized should a strong quake occur. 

He cited an example saying, “if a 30-meter thick sediment is affected by a strong quake, and its maximum compaction is only 1 meter, then no more than only one meter will submerge.”

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