DAVAO DEL SUR – An expert from the Philippine Institute of Volcanology and Seismology (Phivolcs) advised residents of Mindanao that they should not be complacent, and continue to be prepared after four strong earthquakes from October caused major damage in Davao del Sur and Cotabato provinces.
Philvolcs supervising research science specialist Jeff Perez said that the Tangbulan fault, stretches 62 kilometers from Davao del Sur to Davao Occidental, could generate powerful earthquakes up to magnitude 7.2.
“May mga mangyayaring aftershocks, and this aftershocks will die down habang tumatagal. Talagang magde-decrease ‘yan day by day. But we don’t remove the possibility na magkakaroon ulit ng isang malakas na lindol,” he said.
Phivolcs is looking into the possibility that the three earthquakes measured over magnitude 6 in October, might have occured along the Makilala-Malungon fault.
The agency said residents should strengthen their preparedness and ensure structural integrity in the rebuilding or retrofitting of new and existing houses and buildings.
“So dapat patuloy yung ginagawang preparedness, baka magiging kampante ang mga tao after this event. Magpatayo na naman sila ng bahay. Dapat yung matibay na,” he said.
PADADA: LIQUEFACTION-PRONE AREA
Experts discovered two long liquefaction areas that stretches few blocks in Padada town proper.
Perez said the soil in the areas between quake-generated cracks even subsided up to 40 centimeters, causing the structures to sustain major damage.
“Sana in the future, we can explain kung bakit nag-subside ‘to, bakit nagkaroon ng mga fissuring. Alam natin na halos buong Padada, ay dahil sa malapit sa ilog at dagat, malambot ang lugar dito at liquefaction-prone area.”
Sandboils, or water that bursts from the ground like a fountain, were also spotted in the town proper.
“Ang sandboil ay nangyayari sa malambot na lugar, na malapit sa ilog, malapit sa dagat. Yung sediments nila sa ilalim ay sand. So sandy siya, may tubig. Pag inalog mo siya, yung water, mag-settle sa tubig. Lalabas yung water together with sand.
LESSONS LEARNED
Municipal engineer George Claud said they will strictly monitor local structures.
He advised residents that before they build a house or a building, it is recommended that soil exploration should be done, not be stingy with construction materials, and hire an independent or private engineer.
Three powerful quakes struck the region in October, leaving at least 23 dead and dozens injured.
In addition, 11 died after the 6.9-magnitude earthquake in Davao del Sur last Wednesday.
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