Abstract
The survey of earthquake-undamaged structures is regarded as important for the progress of earthquake engineering as that of earthquake-damaged structures. Actually however, there are few survey of undamaged structures due to earthquakes. Through the investigation of the complete survey which contains both damaged and undamaged data, it could be understood which case is susceptible to damage for a structure and also which case is not. From this point of view, the complete survey of damaged and undamaged small earth dams for irrigation in Aomori and Akita prefectures due to Nihonkai-Chubu Earthquake in 1983 were carried out by distributing relevant questionnaires, from which a total of 1129 data on the irrigation dams were used for a series of analysis. On the basis of the data of this survey, two different damage ratios were compared in this study. One is the ratio of the number of damaged dams which could be obtained even from the survey of damaged dams, the other is, so to speak, “the damage ratio” which was obtained only from this complete survey. Two ratios were investigated in detail and the significance of such a complete survey was discussed.
