Liquefaction as an important source of the A.D. 2011 Tohoku-oki tsunami deposits at Sendai Plain, Japan

This paper describes the topographic change and the recovery process, as well as the sediment sources, for tsunami deposits based on fi eld surveys and analysis of digital elevation model data before and after the A.D. 2011 Tohoku-oki tsunami at the Sendai Plain, Japan. We found that the amount of sediment deposited on land was approximately four times greater than the eroded volume of sediment at the beach. Large amounts of the sediments deposited at the studied transect probably originated from liquefaction. This result suggests that the vented sediments might have been an important source of the tsunami deposits if liquefaction is generated by the strong ground motion of a near-fi eld earthquake. In contrast, minor erosion was observed at the beach, and the beach berm was rebuilt within three months after the tsunami. Moreover, the erosional channel that had cut into the beach had been fi lled by sand within 13 days after the tsunami. Therefore, it is not expected that a sedimentary record of the tsunami will be preserved in the nearshore zone along the Sendai coast, although remnants of small scours on land might remain long after the tsunami.