Abstract:
Disasters cause serious economic and human losses. Therefore, damage assessment is needed to support post-disaster management, humanitarian assistance, and disaster relief. This research focuses on applying the coherence change detection technique with Sentinel-1 data for damage assessment of urban areas of four cites. The first three cities affected by a natural disaster including Antakya, Iskenderun, and Adana in Turkey which affected form the two earthquakes of magnitude 7.8 and 7.5 occurred nine hours apart in south-eastern Turkey near the Turkey-Syria border on 6 February 2023. Another city affected by a human-caused disaster which is Mariupol, a city in the south-eastern Ukraine affected by the conflict between Russian and Ukraine since 24 February 2022 until the city was fully controlled by Russia in late May 2022. For each study area, images of three months before the event were used. We used the images from November 2021 for Ukraine and November 2022 for Turkey. These images of three months until the last image before the event represent late autumn and winter seasons and were used to generate an average pre-event coherence image for each study area. Then, we applied a log ratio to the average pre-event and post event coherence image to find the intensity of coherence changes after the event occurred in each study area. The results showed that the pre-event coherence of urban areas was high then turned to low after the earthquake, especially in Antakya, which was one of the most affected cities as the coherence decreased in all over the city, while Iskenderun showed loss of coherence mostly in the north-western part of the city as it was less affected than Antakya. The coherence of Adana slightly decreased as this city was least affected by the earthquake compared to the two cities. In Mariupol, there were gradually changes in the beginning of the invasion, then a lot of changes occurred in middle March to middle May 2022 and the most intense changes happened in the city centre and the Azovstal industrial site. However, there also were widespread changes all over the urban areas. The total area of Antakya affected by the earthquake was the most, at 44.58%. Iskenderun had the total affected area, at 24.09% and Adana had the least affected area at, 7.79%. In Mariupol, 44.88% of the urban area was affected by the conflict from the beginning of the invasion until June 2022. The coherence change detection technique with Sentinel-1 Imagery is a useful method in applying for damage assessment that can be used immediately during the early and critical state of disasters. It is suitable to identify changes in urban areas but not suitable to apply in areas that covered with vegetation.