A sparsely documented tsunami in 1454 may subdivide the recurrence interval between the 869 and 2011 tsunamis near Sendai, as judged from geomorphic, stratigraphic, and archival evidence. Pond‐filled breaches cut across beach ridges on century‐old topographic maps. The basal pond deposit in one of these breaches postdates 1454. Stratigraphy on Sendai Plain includes a sand sheet that contains marine and brackish diatoms. Radiocarbon ages suggest that the sheet dates to 1406–1615 (2σ), and written records for this interval in Tohoku mention a tsunami in 1454. The inferred inundation extended 1.0–2.5 km inland from an approximate medieval shoreline. Simulated tsunamis that best account for the sand sheet require a thrust earthquake of moment magnitude 8.4 or larger. If the sand sheet represents the 1454 tsunami, the two most recent intervals between great thrust earthquakes in Sendai region spanned 585 and 557 years.

This study presents relative sea-level (RSL) change from 11,200 to 500 cal. BP in the Toyooka Basin, western Japan. Diatom assemblage and sedimentary sulfur analyses were performed for 32 sediment cores obtained from thick Holocene fluvial and marine deposits. An age model was constructed based on tephrochronology and 31 radiocarbon ages from elevations of −46.85 to +1.51 m in 19 cores. The RSLs in the Toyooka Basin are −31.05 m in elevation at 10,000 cal BP, above −4.00 m at 7900 cal. BP, −0.47 m at 6700 cal. BP and +0.15 m at 3300 cal. BP. A rapid sea-level rise, at a rate of about 23 mm/yr, is observed during the period from 10,600 to 10,300 cal. BP. Relative sea-level rose at a rate of about 12 mm/yr between 10,000 and 7900 cal. BP. The rate of sea-level rise decelerated at 7900 cal. BP, from about 12 mm/yr (10,000–7900 cal. BP) to 3 mm/yr (7900–6700 cal. BP). The mid-Holocene sea-level highstand probably occurred between 7000 and 6000 cal. BP, but it remains difficult to constrain its elevation. These RSL features described here may provide a typical example of Holocene sea-level changes resulting from both eustatic and hydro-isostatic components for the Japanese islands.

To assess long-term tsunami inundation history, we studied a wetland on the Pacific coast of Aomori, Japan, at the northern end of the Japan Trench. We found five sand sheets interbedded in freshwater mud and peat, three of which contained brackish diatoms indicating deposition by marine inundation. We identified the youngest sand sheet, deposited AD 1480-1770, as a tsunami deposit based on its lateral extent (>1 km) from the shoreline at the time of its deposition. Although this area has been struck by many tsunamis generated by earthquakes along the Japan Trench as well as along the Kuril and Peru-Chile trenches, no tsunami recorded at least in the past 120 years has inundated the coast as far inland as this tsunami deposit is distributed. We therefore infer that it was deposited by an unusually large tsunami. Historical and geological evidence for tsunamis in north-east Japan suggests that possible sources are the AD 1611 Keicho earthquake along the Japan Trench, a 17th-century earthquake along the Kuril Trench, or an unknown large earthquake.