Study on casualties of Dujiangyan City in Wenchuan earthquake

Dujiangyan City suffered heavy casualties in Wenchuan earthquake.This paper studies the spatiotemporal distribution characters and factors impacting casualties of this city to provide some reference for urban earthquake disaster mitigation.Based on the earthquake intensity and casualty data of each town,the effects of earthquake intensity and population density on death rate are analyzed,and the empirical expressions are given.The result shows that there is an obvious positive correlation between mortality rate and earthquake intensity.The change of death rate with fault distance is studied,and it's shown that the correlation between death rate and fault distance is higher than the correlation between death rate and earthquake intensity.To some extent,estimation of death rate based on fault distance reduces the human caused uncertainty in intensity evaluation,which is thus more objective.The changes of the number of reported deaths with time are quantitatively analyzed,and the effects of rescue efficiency on the reported deaths are qualitatively discussed.The ratio of reported deaths to total deaths is proportional to rescue efficiency.By summarizing several factors causing casualties,it is shown that destruction and collapse of building structures are the main reason of casualties,and the death rate caused by building damage depends on the building type.Attention should be paid to this issue when estimating the casualty rate.