On March 11, 2011, Japan's largest island, Honshu, was struck by a magnitude 9 earthquake. It was triggered by a convulsive release of tension that had built up through the collision of the Pacific Plate with a spur of the North American Plate. The epicenter was located 70 km off the coast, and parts of the island, the shelf, and the continental slope were shifted up to 50 m toward the east, and the sea floor was lifted by up to 5 m. As a result of these movements, including possibly large submarine slumps, a tsunami up to 40 m high was created that devastated broad segments of the coast and claimed around 15,000 human lives. The earthquake region shall be investigated by a joint German-Japanese expedition of the RV SONNE in March-April 2012, using a ROV, AUV, multibeam, parasound, gravity corer and multicorer in order to determine the changes caused by the earthquake, recover buried instruments, and retrieve sediment cores. The results will contribute to a better understanding of the course of events and the mechanisms of the earthquake and tsunami.