How Many Lives were Saved by the Evacuation

It is difficult to know how many fatalities and injuries in an earthquake may have been avoided by a mitigating action because the result without the mitigation can usually not be estimated with a useful reliability. The case of the evacuation before the 1975, M 7.3, Haicheng earthquake offers a rare opportunity to quantitatively estimate the number of casualties saved. We show that the computer tool QLARM has calculated the human losses in eight damaging earthquakes in China approximately correctly within 40 min, without information from the affected area. Therefore, our estimates of the numbers of casualties that would have resulted in the Haicheng earthquake without evacuation are reasonably reliable. The numbers of fatalities and injured saved are estimated to have been about 8000 and 27,000, respectively, ( 60%). We propose that advanced scenario modeling of the losses in disasters, natural or man-made, allow estimates of the effectiveness of mitigation. Evaluation of the effectiveness of countermeasures for disaster risk reduction in saving lives is a seemingly impossible job, although it plays an important role in the review and improvement of the preparedness for and mitigation of disasters. With new data accumulated and new tools developed, this becomes feasible to some extent for some cases. In this report, we select a specific disaster (a damaging earthquake), a specific time scale (short-to-imminent term), and a specific countermeasure (evacuation based on a forecast). The unique case of the 4 February 1975 Haicheng earthquake (Wang et al., 2006) offers the opportunity of evaluating the effectiveness of the mitigation taken. The prediction of, and evacuation before, this wellknown earthquake has been controversial (Hammond, 1976, Geller et al., 1997); and the varied reports of deaths (1326 [Quan, 1988]; 2041 [Wang et al., 2006]; or only a few [Davies, 1975]) during this earthquake further added to the debate on whether or not the forecast and evacuation really saved a substantial number of lives. Here we estimate quantitatively how many lives may have been saved and how many injuries prevented by the timely evacuation before the M 7.3 Haicheng, China, earthquake of 1975.