Estimation of earthquake casualties using high-resolution remote sensing: a case study of Dujiangyan city in the May 2008 Wenchuan earthquake

From a disaster relief perspective, an immediate and efficient rescue operation after an earthquake can greatly increase the number of survivors. An effective rescue operation depends on two key elements: localisation of the affected areas and estimation of the number of casualties in these areas. Many more studies have been conducted on the localisation of affected areas than on casualty estimation. Consequently, this study develops a model for rapidly estimating the number of casualties using satellite remote sensing (SRS). The model is based on the attributes of damaged buildings, as these buildings cause the greatest harm to inhabitants and they can be detected by SRS. The model uses the damage index (DI) of buildings computed by a numerical damage model derived from SRS images to assess the extent of damage. The DI is then combined with the building's materials and structure index, which is calculated using information from the local geographic information system, to compute the joint casualty index (JCI). Finally, the number of casualties is estimated by the product of the JCI multiplied by the number of people inside the damaged buildings at the time of the earthquake. The model is then applied to three towns in Dujiangyan City, as these were the areas that most severely affected by the Wenchuan earthquake. Preliminary results showed that there was little difference between the actual and estimated number of casualties. It is recommended that more casualty data should be included in the model to improve the accuracy of estimation.