兵庫県南部地震による北淡町を中心にしたため池の被害の要因分析

This study was performed to clarify which factors affected damage to take-ike (small embankment dams for irrigation in Japanese) of Hokudan Town on Awaji Island in western Japan due to Hyogoken-Nambu earthquake. Multivariate and ordinary statistical analysis were carried out using documentary data (181 damaged and 328 undamaged dams), and ordinary one was done for the results investigated in situ. The model for the multivariate analysis was created with 13 items and 94 categories for 4 groups (Location, Geology Structure, and History of Dam). As a result, the factors causing to damage for dam are (1) the nearest fault (Nojima, Mizukoshi and D2), (2) embankment volume (the larger the more), (3) angle of crest axis to epicenter (diagonal and normal), (4) distance to the nearest fault (less than 500 m), (5) distance to the epicenter (8 to 14 km which almost agree to the location of seismic intensity 7 JMA), (6) play view of dam axis (3 or 4 axes), (7) angle of crest axis to nearest fault (diagonal and normal), (8) elevation of dam site (over 100 m), (9) surface geology of dam site (non-cohesive soil), (10) era of construction (prior to 1891), and (11) soil properties of embankment (constructed of sand, smaller penetration resistance).