Damage to coastal structures

Abstract

On March 11, 2011, the largest earthquake ever recorded in Japan struck off the coast of the Tohoku region of the country, and was subsequently named the 2011 off the Pacific coast of Tohoku Earthquake by the Japan Metrological Agency. The Mw 9.0 earthquake generated strong motions that affected the island of Honshu from Tokyo Bay to the northern extent of the island, and induced a series of tsunamis that devastated coastal communities throughout the region. Significant aftershocks (Mw>7) were experienced that further contributed to damage in the coastal Tohoku region during emergency response and recovery efforts. This paper summarizes the findings of the Port and Airport Research Institute (PARI) research team as it investigated coastal structures along approximately 600km of coastline as well as the team׳s follow-up experiments and analyses. Two characteristics of the ground motion observed were the long duration and the high-frequency component. For this reason, the degree of damage caused to coastal facilities by the ground motion was relatively small. The wide-ranging investigation by the PARI team facilitated the interpretation of damage patterns across the entire region affected by the earthquake, with a primary goal of distinguishing damage to coastal structures resulting from strong ground shaking and secondary effects (such as liquefaction, ground failures, and settlement) from that caused by the subsequent and significant tsunami inundation.