Geotechnical Problems in the 2011 Tohoku Pacific Earthquakes

An overview of the geotechnical aspects of the building damage in the 2011 Tohoku Pacific earthquake is presented, based on field reconnaissance made after the quake. It is shown that: (1) Extensive soil liquefaction occurred along the coast of Tokyo Bay and around the Tonegawa River floodplain. Liquefaction primarily occurred within relatively new reclaimed area, with large ground settlement up to 60 cm, accompanied by settlement/tilting of wooden and reinforced concrete buildings supported on spread foundations; (2) Numerous houses in Sendai’s hilly residential areas constructed with cut-and-fill methods were badly damaged not only by simple collapse of retaining walls, but also by slope failures of fill; (3) Several pile-supported buildings tilted and settled not only in the Tohoku region but also in the Kanto plain, implying damage to pile foundations; and (4) Several steel and reinforced concrete structures in Onagawa were knocked over by tsunami surges, probably after having suffered damage to their pile foundations.