Dam Failure Case Study: Fujinuma Dam (Japan, 2011)

On March 11, 2011, a massive 500-600 km rupture off the east coast of Japan resulted in a powerful Magnitude 9.1 earthquake and subsequent tsunami. The shaking also damaged at least 745 dams in Fukushima Prefecture and caused a rare seismically induced failure of the Fujinuma Dam. The earthfill dam and an earthfill saddle dam were built in layers from 1937 to 1949 to store irrigation water.
Observations and analyses concluded the dam had poor compaction and foundation treatment, likely resulting in a seismically induced slope failure that lowered the crest below the reservoir level. The saddle dam and multiple slopes around the reservoir rim also had slope failures, likely due to rapid drawdown.