This paper discusses the reduction effect of a foreshock on casualties during the mainshock of people who evacuated to shelters and their private cars during the 2016 Kumamoto earthquake. In the first part of this paper, we discuss the number of human casualties caused by the collapse of wooden buildings. The characteristics of casualties in the Kumamoto earthquake are classified as household attributes and building damage caused by the foreshock and mainshock. In the second part, we apply equations (Nakashima and Okada 2008 and Okada and Nakashima 2015) to the Masiki area to determine the total number of casualties with a focus on deaths. The number of deaths due to total building damage from the foreshock and the mainshock in the case of 0 evacuees was estimated as 147. We then estimated the reduction effect on the number of casualties caused by the foreshock by using the survey data of the mainshock and foreshock. We found that evacuation during the mainshock decreased the death toll by 128 people. Moreover, the number of injured people decreased by 657. Generally, most people who evacuate tend to return home over time. As a result, many people die at the time of a subsequent mainshock. It is important to provide death risk information to each household to support their decision-making regarding appropriate evacuation.

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