Damage Mapping of the Hunga Tonga-Hunga Ha’apai Volcanic Eruption and Tsunami on the Tongatapu Island Using Satellite Imagery

On 15^th January 2022, a large eruption of the Hunga Tonga–Hunga Haʻapai (HT-HH) undersea volcano of the Kingdom of Tonga, generated a tsunami triggering evacuations at local and regional scales in the Pacific Ocean. In this work, we used optical (Sentinel-2, Landsat 8/9, and WorldView-3) and SAR (ALOS-2 PALSAR-2 and Sentinel-1) images taken before and after the event to map the tsunami damages and ashfall debris in Tongatapu, and Atata Island. The results showed that the areas covered by ash within two weeks after the event were more than 80% of the total area, whereas two months later, it dropped to 10%. The average Normalized Difference Vegetation Index (NDVI) before the volcanic eruption was 0.8, and after the volcanic eruption, it reduced to 0.35 in Tongatapu, and 0.23 in Atata Island, which was severely hit by the tsunami. The object-based analysis of WorldView-3 data showed a more accurate estimation of the damage to the buildings and vegetation.