The 11 March 2011 East Japan Earthquake and Tsunami: Tsunami Effects on Coastal Infrastructure and Buildings

This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/24.The 11 March 2011 East Japan Earthquake and Tsunami caused unprecedented\ud damage to well-engineered buildings and coastal structures. This report presents some notable\ud field observations of structural damage based on our surveys conducted along the Sanriku coast\ud in April and June 2011. Engineered reinforced concrete buildings failed by rotation due to the\ud high-velocity and deep tsunami inundation: entrapped air in the buildings and soil liquefaction\ud by ground shaking could have contributed to the failure. The spatial distribution pattern of\ud destroyed and survived buildings indicates that the strength of tsunami was affected significantly\ud by the locations of well-engineered sturdy buildings: weaker buildings in the shadow zone\ud tended to survive while jet and wake formations behind the sturdy buildings enhanced the\ud tsunami forces. We also found that buildings with breakaway walls or breakaway windows/doors\ud remained standing even if the surrounding buildings were washed away or destroyed. Several\ud failure patterns of coastal structures (seawalls) were observed. Flow-induced suction pressure\ud near the seawall crown could have caused the failure of concrete panels that covered the infill.\ud Remarkable destruction of upright solid-concrete type seawalls was closely related with the\ud tsunami induced scour and soil instability. The rapid decrease in inundation depth during the\ud return-flow phase caused soil fluidization down to a substantial depth. This mechanism explains\ud severely undermined roads and foundations observed in the area of low flow velocities