Geoengineering and Seismological Aspects of the Iwate-Miyagi-Nariku, Japan Earthquake of June 14, 2008

The Iwate Miyagi-Nairiku earthquake occurred in an interior and rural mountainous region of Tohoku, Japan in steep terrain. Geoengineering damage was almost entirely confined within a 35-km radius of the epicenter. Landslide impacts to transportation infrastructure and moderate deformations of earth dams provide some of the most important geoengineering case histories for the Iwate Miyagi-Nairiku earthquake. Remarkably, there were no observations of liquefaction from this event.

Reservoirs and dams performed well during the earthquake. The team visited seven earth and concrete dams during the field reconnaissance. Deformations and damage to concrete dams was minimal, although several instances of landslides entering reservoirs occurred and provide case histories of landslide induced seiches in reservoirs. Several earthen dams suffered moderate deformations due to settlement of the crest. These provide excellent case histories of seismically-induced earth dam deformations. One large earthen dam, the Aratozawa Dam in Miyagi Prefecture, had a large landslide impact the reservoir sending water over the spillway. Nowhere in a central area did a dam fail. At one dam, the Isawa Dam in Iwate Prefecture, one worker was killed by rockfall at the dam abutment. Landslide impacts to reservoir waters and moderate deformations of earth dams provide some of the most important geo-engineering case histories for the Iwate-Miyagi Nairiku earthquake.