The Philippine Space Agency (PhilSA) reported on Saturday that it is analyzing satellite data to map areas that may have been affected by landslides following the recent magnitude 7.8 earthquake in Mindanao.

The agency identified possible earthquake-induced landslide areas in the barangays of Calabanit, Ilaya, San Vicente, Congan, and Calpidong in Glan, Sarangani, as well as Butuan, Patulang, Sugal, Nuing, San Isidro, and Batulan in Jose Abad Santos, Davao Occidental.

“The total area possibly affected by landslides is about 137.87 hectares (approximately 1.38 square kilometers), or more than half the land area of Bonifacio Global City,” PhilSA said.

The agency said the landslide areas were identified by observing vegetation loss between pre-disaster images taken on June 1 and post-disaster images captured on June 14 using the European Space Agency’s Sentinel-2A and Sentinel-2B satellites.

According to PhilSA, areas that appeared green and vegetated in pre-disaster images but turned brown in post-disaster images indicate exposed soil and were classified as possible landslide sites.

“Vegetation loss was quantified through a significant decrease in the Normalized Difference Vegetation Index (NDVI) between the satellite images. The maps are subject to ground validation,” the agency said.

PhilSA added that the satellite data supports the National Disaster Risk Reduction and Management Council (NDRRMC) in monitoring the situation and prioritizing areas for response.