The March 9th 2011 earthquake of Mw=9, that occurred offshore NE Japan, triggered major tsunami waves that affected almost all of the NE coast of Japan and caused massive casualties. Great damages were observed as whole residential, industrial and rural areas were swept away. Preliminary field observations on the behaviour of different types of structures and critical infrastructure are presented, the causes are analyzed and comparisons are made with the damage caused by the tsunami of Indian Ocean of December 26th, 2004.