Yuichi Niwa

Geomorphology and Tectonic Setting of the Sanriku Coast, Northeastern Japan, and Introduction of Recent Studies on the Formation of Alluvial Plains and Holocene Crustal Movements Along the Coast

The 2011 Tohoku-Oki earthquake dramatically changed the coastal environment along the Pacific coast of northeastern Japan. In particular, coseismic subsidence of up to 1.3 m was recorded along the Sanriku Coast . However, well-preserved Middle to Late Pleistocene marine terraces along the northern Sanriku Coast have been interpreted to indicate uplift since the Late Quaternary. This discrepancy between long-term uplift and short-term subsidence has been attributed to coseismic uplift during an unidentified megathrust earthquake. To clarify the interplay of uplift and subsidence, we introduce the tectonic setting of the Sanriku Coast and recent studies on the geomorphology and geology along the coast, which focus on crustal movements during the Holocene along the southern Sanriku Coast. The results of recent studies indicate that, contrary to the previous view that the northern Sanriku Coast has experienced long-term uplift, the southern Sanriku Coast has been subsiding since the 10 ka (since the latest Pleistocene).