UP National Institute of Geological Sciences (NIGS), UP Resilience Institute (RI) sends Quick Response Team to Assess October 2019 Cotabato Quakes
Written by Audrei Anne B. Ybañez and Richard L. Ybañez
Last 7 to 11 November 2019, geologists from the University of the Philippines National Institute of Geological Sciences, through the UP Resilience Institute UP RI, assessed the geologic impacts of the series of high-magnitude earthquakes (magnitudes > 6.0) that struck the province of Cotabato last October 2019. This was conducted in response to a formal request by acting Cotabato Vice-Governor Shirlyn Macasarte-Villanueva for assistance from the University of the Philippines.
The UP Geology team was composed of UP RI Executive Director Alfredo Mahar Lagmay Ph.D., UP RI Director Genaro Cuaresma, UP NIGS Director Mario Aurelio Ph.D., UP RI Researcher Audrei Anne Ybañez, UP NIGS Instructors Richard Ybañez and Yvonne Ivy Doyongan, UP NIGS Researchers Criselda Baldago and John Agustin Escudero, and NIGS SG&T Researcher Iris Yvette Cesista. The team of geologists from UP inspected affected areas where earthquake-related hazards like liquefaction and landslides have occurred, validated safe areas for existing or potential relocation sites, and studied the faults that may have caused these devastating earthquakes.
UP Geology Team during consultations and meetings with LGU and Incident Management team in Cotabato.
To assess the geologic impacts of the earthquakes, the UP Geology team went to barangays Batasan, Biangan, Kisante, Malasila, and Buenavida in Makilala, Cotabato. Landslides, tension cracks, and fissures were widespread in these areas. These structures also traversed roads, highways, and houses resulting to further damage.
Widening of tension cracks upslope in Brgy. Batasan. The sketch diagram shows a schematic cross section of the slope. Aftershocks and rainfalls could worsen the cracks and could eventually lead to a landslide.
Site inspection of existing and potential relocation sites was also conducted by the team in order to ensure the safety of the communities affected by the recent earthquakes. The proposed sites are located in Brgy. Gasika, Brgy. Buenavida, Brgy. Batasan, and the DOLE-STANPHILCO Plantation based on geologic hazard investigation and NOAH landslide and flood hazard maps. All of these areas were located in generally flat to rolling terrain clear from tension cracks and with no nearby fault zones. Areas with observed landslides, tension cracks, and liquefaction should be monitored closely for future incidents. Rebuilding within these zones is not advised.
Aerial imagery of potential relocation site for Barangay Garsika.
NOAH landslide hazard map of Barangay Garsika
The UP Geology team is also investigating the possible presence of an unmapped and undiscovered fault within the Municipality of Makilala. This hypothesis is based on gathered geologic data in the field, satellite imagery, and computer models. These computer-based data and models suggest a northeast-trending fault stretching from Brgy. Luayon in the southwest, traversing Brgy. Batasan to the northeast. Research is currently ongoing to determine the presence of this fault and the possible hazards it may entail.