Seismic-driving of sand beach ridge formation in northern Honshu, Japan?

Abstract

Abstract The coastal Sendai Plain consists of an extensive sand beach ridge system that was inundated by the 2011 Tohoku-oki tsunami. The spatial and temporal extent of these beach ridges appears to match well with the record of past earthquakes and tsunamis in the region and it is proposed that they could have formed as a result of a process called “Seismic-Driving”. This process recognises the widespread and catastrophic disruption of the environment caused by a large earthquake. A series of immediate and delayed after-effects created by a cascade of geomorphological processes linking the earthquake with beach ridge formation is examined for the Sendai Plain. The significance of the role played by volcanic eruptions, smaller earthquakes and climate-related, high intensity and duration rainfall activity is also highlighted. At a region-wide scale, the beach ridge systems of Ishinomaki, Akita, Aomori and Tanabu are also considered alongside those of the Sendai Plain. Throughout northern Honshu there appears to be synchronous beach ridge formation, albeit based upon a moderately poor chronological resolution. Further data indicate that there may also be contemporaneous evidence on Hokkaido to the north. More detailed research is now needed in order to secure a higher resolution dataset of the spatial and temporal extent of beach ridges throughout the region in order to determine whether they preserve a record of the magnitude and frequency of earthquakes (and potentially tsunamis) related to activity on both the Japan and Kuril Trenches. If strong seismic-driving linkages can be proven it offers the intriguing possibility of being able to develop a far more comprehensive record of past earthquakes and tsunamis (local, regional and distant) than currently exists. Records could be based on both tsunami deposits in the low-lying swales and the spatial and temporal extent of the intervening beach ridges.