Integration of gravity and geospatial data to determine geological hazard prospect zones in the Halmahera, North Molucca using GIS Weighted Overlay Index (WOI) method

Halmahera Island is one of the Indonesian archipelagos that formed from the interaction among three major plates, Indo-Australian, Eurasia, and Pacific. This convergence causes Halmahera Island presumably to be a geological hazard susceptibility area. This study used gravity data to delineate subsurface structure based on the Euler Deconvolution technique and further combined with various geospatial data, including lineament density extracted from Sentinel-1A imagery, rainfall rate, PGA, and vegetation index (NDVI) derived from optical imagery processing, to generate a geological hazard potential zone map based on the Geographic Information System (GIS) implementation. Each thematic map is weighted using the Analytical Hierarchy Process (AHP) approach, normalized by the Weighted Overlay Index (WOI) technique, and summed up to calculate the Hazard Potential Index (HPI). The calculated map is ranked and reclassified as the most and least dangerous zone of geological hazard vulnerability. HPI shows the most dangerous area is located in several places, including the north and south arms of Halmahera with an index of 0.63 and 0.51, respectively, while the lowest potential zone is in the southeast arm (0.15). The outcome of this mapping is presumably to be used as a hazard mitigation reference henceforward.