Geologic Influences on Sinkhole Morphometry in Siargao Island, Surigao del Norte, Philippines

Abstract. The 2013 Bohol earthquake and other phenomenon has caused numerous sinkholes to emerge in several areas specially in karstic regions, leaving a significant gap in research concerning sinkholes, especially in the Philippines. In an island primarily composed of carbonate materials like Siargao Island in southern Philippines, it becomes imperative to understand the potential geological hazards that may arise in karstic regions. This study utilizes remote sensing techniques, including IfSAR-DEM, processed in GIS platform, to evaluate sinkhole hazards. It involved detailed geological and geomorphological assessments, considering factors like sinkhole distribution, lineaments, streams, elevation, and formational units. The methodology includes using sinkhole inventory from Mines and Geosciences Bureau - Region XIII in locating high-risk areas. The resulting maps depict regions prone to subsidence, particularly where sinkholes can form unexpectedly. The study shows four key factors influencing sinkhole occurrence in the island such as lineaments, elevation, slope, and karstic bedrock. Majority of sinkholes are found in low elevation, gentle slope, and proximal to lineaments (200-400m). The findings of this investigation will not only contribute to a deeper comprehension of the geological forces influencing the island's topography but also provide valuable insights for better land-use planning and risk mitigation in this region, where such geological phenomena can have significant implications for local communities and infrastructure.