Abstract:
An earthquake measuring 6.6 Mw struck southern Hokkaido, Japan, September 2018. Mizuho Dam and Azuma Dam were located near the epicenter of this earthquake
and strongly shaken. The recorded base peak accelerations of Mizuho Dam in upstream and
downstream directions was 491 gal and 937gal was recorded at dam crest. Maximum settlement of crest at upstream slope side was about 12cm and cracks attained about 2.0 m depth
were observed around the crest. Azuma Dam’s spillway was blocked by debris from landslides. Recorded base peak acceleration was 297 gal and 1293 gal was recorded at dam crest.
A simple strain softening elasto-plastic constitutive model is applied to both dams with the
features of non-associated flow characteristics, post-peak strain softening, and strainlocalization into a shear band with a specific width. The dynamic response analyses of both
dams and the computed settlements are compared to observed one.
