Daven Tamayo

Is the new land in Sarangani following earthquake safe for building?

Article (news)

Raphael Bosano

ABS-CBN News

<div><img src="https://od2-image-api.abs-cbn.com/prod/editorImage/17819470767351781947082868.jpeg" style="width:960px" class="fr-fic fr-dib" width="960"/>DENR Soccsksargen photo</div>MANILA — Following the recession of tides and the appearance of additional patches of land in several parts of quake-hit Sarangani Province, the Department of Science and Technology reminded the public to avoid building structures on them.At the sidelines of the National Nutrition Summit in Pasay on Wednesday,  DOST Secretary and former PHIVOLCS Director Renato Solidum said it isn’t wise to build any structure on top of the new patches of land that appeared after June 8’s devastating earthquake as this area is particularly prone to storm surge and tsunamis. “Kasi nga dating coastal area yan. So ibig sabihin near the shoreline so prone ka sa many hazards,” he said.Based on maps generated by the Philippine Space Agency, shifts in the shoreline were seen in Barangay Burias and Barangay Pangyan in the town of Glan, Sarangani. Pre and post earthquake delineation shows a wider shoreline in some parts. The PSA defines a shoreline as the boundary of the exposed sand.  There are also possible underwater features that have been exposed following the tremors. But the PSA emphasized that their maps are subject to ground validation. <div><a href="https://www.abs-cbn.com/news/nation/2026/6/19/deped-clears-most-region-12-public-schools-to-resume-classes-after-earthquake-1524">DepEd clears most Region 12 public schools to resume classes after earthquake </a> </div>What happened? The change in the shoreline is not unusual especially following a shift in the ocean floor.Experts call it a coastal uplift from the movement of the Cotabato Trench. Solidum explains that during an earthquake, large chunks of rock collide with some sliding on top of another.“Ang Cotabato Trench ay sumusuksok pa ilalim ng Celebes Sea at nagsisimula yung pagsuksok sa Cotabato Trench. Kapag nagkaroon ng pagsuksok, hindi yan dumudulas lang. Nagkakaroon ng friction kasi bato yan ang nag-interact. Kapag sumubsob yan, nagkakaroon ng bukol dito,” he said.This phenomenon displaces seawater, produces tsunami waves and permanently alters the coastline. This permanent change inevitably affects biodiversity. Grick Cordero, Senior Ecosystems Specialist of the Department of Environment and Natural Resources, explains the corals that have emerged from the beneath the ocean will eventually die and possible alter the composition of species in the portion of the ocean where the coastal uplift happened.<div><a href="https://www.abs-cbn.com/news/regions/2026/6/14/deadly-mindanao-quake-raised-seabed-by-up-to-two-meters-1710">Deadly Mindanao quake raised seabed by up to two meters</a></div>“Kung malaking parte yun ng coral reefs before, for sure naging importante yung for a very long time kasi maaring doon nangingitlog yung mga isda, nagpapalaki,” he said.While the coral void beneath the ocean following the uplift he adds, will eventually be replaced as baby corals eventually find their place. But, like trees, it usually takes years, even decades, for them to fully mature and provide ecosystem services like fish habitat and breeding sites. Coastal uplifts are not new.The DOST said following the Bohol earthquake in 2013, one side of Bohol facing Cebu experienced subsidence while another portion, including the town of Maribojoc, rose. <div> </div><div>EFFECTS ON HUMAN SETTLEMENTS</div>While the coastal uplift will inevitably affect marine biodiversity in that part of the ocean in Sarangani, Solidum said it isn’t seen to highly impact human settlement.“The human community is not affected because they will be added to the land area in the long term. But essentiall they biodiversity will adjust.”However, he advises communities living near that portion of Sarangani to avoid building on top of the corals that emerged due to the uplift. Aside from being prone to tsunami waves and storm surges, the new patch of land that emerged is said to not be strong enough to hold enormous amounts of weight.<div><a href="https://www.abs-cbn.com/news/regions/2026/6/8/mindanao-quake-caused-by-cotabato-trench-phivolcs-1135">Mindanao quake caused by Cotabato Trench — Phivolcs</a></div>“Corals, when underwater, grow. But once they are uplifted, prone yan sa disolusion. Pagpatay na yung corals, ang limestone lang yan eh, calcium carbonate, pwede siyang matunaw. So yung iba dyan, pwede magkaroon ng butas. Kaya may mga sinkhole na napo-form sa gano&#x27;ng mga klase ng bato,” he said. Metro Manila earthquake not confined to movement of West Valley Fault aloneThe National Simultaneous Earthquake Drill came just a little over a week following Mindanao’s devastating earthquake.What is usually highlighted during these exercises are worse case scenarios of a 7.2 magnitude earthquake from the movement of the West Valley Fault. However, Solidum said another scenario may also happen — the occurrence of an ocean earthquake due to the movement of the Manila Trench. This event, he says, may trigger tsunami waves and cause massive flooding in an already vulnerable metropolis.The movement of the Manila Trench may generate an magnitude 8 earthquake or higher. But shaking may be weaker as it is offshore. This scenario, along with other strong tremors, makes it even more important for agencies and individuals to exercise utmost responsibility in constructing structures particularly buildings and houses.“The real challenge is making sure na sumunod tayo sa building code,” Solidum said.Newer buildings and houses constructed according to the New Building Code, officials say, have high chances of surviving strong tremors. Those built before it, however, must be checked and retrofitted to increase their chances of surviving major earthquakes.

Following the recession of tides and the appearance of additional patches of land in several parts of quake-hit Sarangani Province, the Department of Science and Technology reminded the public to avoid building structures on them.

Following the recession of tides and the appearance of additional patches of land in several parts of quake-hit Sarangani Province, the Department of Science and Technology reminded the public to avoid building structures on them.