兵庫県南部地震による淡路島北部5町のため池被害・無被害要因の多変量解析  [in Japanese] Multivariate analysis for damage factors of small embankment dams on five towns of northern Awaji Island due to the Hyogoken-Nambu earthquake  [in Japanese]

This study was performed to clarify which factors affected damage to tame-ike (small embankment dams for irrigation in Japanese) of northern Awaji Island in western Japan due to Hyogoken-Nambu earthquake. Multivariate and ordinary statistical analyses were carried out for 1788 dams (350 damaged and 1438 undamaged dams which identified using various documents). The model for analysis was created with 11 items and 136 or 100 categories for 4 groups (Location, Geology, Structure, and History of Dam). As a result of analysis, the factors causing to damage for dam in order are (1) distance to the epicenter (9 to 15km, which almost agree to the location of seismic intensity 7 JMA), (2) nearest fault (Nojima, Mizukoshi and D2), (3) embankment volume (the larger the more), (4) angle of crest axis to epicenter (normal or vertical), (5) angle of crest axis to nearest fault (normal or vertical), especially reservoir located backward dam, (6) distance to the nearest fault (less than 750m), (7) elevation of dam site, (8) plan view of dam axis (complicate), (9) surface geology of dam site (soil foundation), (10) leakage, (11) repair. Analysis in this way might be possible to notice the distribution of intensity of seismic force and prediction for damage of embankment.