Phivolcs Recommends No-Build Zones for Coastal Uplift Areas in Philippines

The Philippine Institute of Volcanology and Seismology (Phivolcs) is recommending that areas experiencing coastal uplifts, which occurred following a Magnitude 7.8 earthquake, be classified as "no-build zones" due to their inherent instability and heightened risk from tsunamis and seismic events. These areas, it is suggested, should be restricted to research and educational purposes. Edward Louise E. Orquillas, Science Research Assistant and member of Phivolcs XI's Project Management and Core Capability Enhancement Team, stated that coastal uplifts are by default unstable ground and are therefore unsuitable for housing. He explained that these areas are also prone to future seismological events, as well as hazardous tsunamis, since they face the sea. "Hindi siya applicable for pabahay, kasi pwede siyang maging tatamaan ng mas further earthquake events or storm surge" (the uplifts are not suitable for housing, because these are vulnerable to further earthquake events or storm surges), Orquillas said. Coastal uplift is a geological phenomenon where portions of the seafloor rise, exposing what were once submerged coral reefs and marine habitats, leading to the alteration of a coastline. The uplifts in various parts of the Soccsksargen and Davao regions occurred due to the June 8 Magnitude 7.8 earthquake. He suggested that these sites could instead be recommended for research and educational purposes. "Pwede siguro gawin for research purposes pero hindi na siya pwede for land use or structural or agricultural or kahit na ano, except yan lang sa research for protected area," Orquillas added. On June 17, the Department of Environment and Natural Resources (DENR) had also warned against building any infrastructure, including houses, on the coastal uplift sites. PNA quoted Karlo Queaño, DENR-Mines and Geosciences Bureau (MGB) Assistant Secretary, as telling Radyo Pilipinas that it is dangerous to live in coastal uplift areas. "Kaya po rito sa Mindanao, importante na, although uplifted, kailangan po nating maintindihan kung ang dagat po eventually ay bumabalik din po. Kaya sa ganitong sitwasyon, we really discourage na ito ay tayuan at mas maganda nga po gawing siyang geologic monument" (So here in Mindanao, it is important that although uplifted, we need to understand if the sea will eventually return. So in this situation, we really discourage building on it, and it would be better to make it a geologic monument), Queaño said. Phivolcs conducted rapid assessments from June 9 to 19 across five provinces, two cities, 21 municipalities, and 110 affected barangays. The team identified 42 coastal uplifts, 52 tsunamis, 127 instances of liquefaction, and damage to 471 structures. The assessment included aerial surveys, field investigations, geologic impacts and hazard assessments, structural damage and intensity surveys, and aftershock monitoring. Phivolcs also installed five temporary seismic stations to enhance continuous aftershock monitoring in Glan and Kiamba in Sarangani, Jose Abad Santos in Davao Occidental, Balut Island, Santo Niño in South Cotabato, and Senator Ninoy Aquino in Sultan Kudarat, according to the Philippine Information Office RXII. The monitoring team comprised geologists, engineers, and social scientists. In Barangay Balangonan, Jose Abad Santos, Davao Occidental, coral platforms approximately 50 meters wide were exposed after a coral bed was raised by as much as 2.5 meters, according to a June 19 post by the Phivolcs-DOST Facebook Page. The Balangonan shore is now located 200 meters farther from its previous position. (Yas D. Ocampo / MindaNews)