COLLAPSE OF SEWAWALL DUE TO THE 2011 GREAT EARTHQUAKE AND TSUNAMI ON ERODING COAST - EXAMPLE OF NARITA AND KAMIGAMA COASTS IN IBARAKI PREFECTURE

Abstract

 On March 11, 2011, a great earthquake and tsunami attacked the Ibaraki coasts. In this period, the seawalls of the Narita and Kamigama coasts, where sand was transported toward the wave shelter zone of Oharai Port and severely eroded, were severely damaged and collapsed mainly due to the ground vibration and their function was lost before the tsunami. The function of the seawall against tsunami was reconsidered.