A great earthquake of magnitude M9.0, occurred around 14:46 pm on March 11, 2011, at an epicenter at an undersea depth of 24 km off the Sanriku coast line, an area in the northeastern part of the main island of Japan. The earthquake was named as "2011 off the Pacific Coast of Tohoku Earthquake." A large-scale fault slide occurred at the plate boundary stretching from the offshore area of Iwate to Ibaraki, and caused heavy tremors of level 7 Japanese Seismic Intensity at Kurihara City in Miyagi Prefecture, and of level 6+ in wider areas in Miyagi, Fukushima, Ibaraki and Tochigi prefectures. This article outlines the outline of the earthquake, and gives an overview of RTRI activities to support the recovery of railway networks damaged by the earthquake. The comparisons of the actual shaking waves of this earthquake with design waves in the Design Standards for Railway Structures: Volume of Seismic Design is also described.