Unusually large earthquakes inferred from tsunami deposits along the Kuril trench

摘要: The Pacific plate converges with northeastern Eurasia at a rate of 8-9 m per century along the Kamchatka, Kuril and Japan trenches. Along southern trench, which faces Japanese island Hokkaido, this fast subduction has recurrently generated earthquakes magnitudes up to approximately 8 over past two centuries. These historical events, on rupture segments 100-200 km long, have been considered characteristic Hokkaido's plate-boundary earthquakes. But here we use deposits prehistoric tsunamis infer infrequent occurrence larger from longer ruptures. Many these tsunami form sheets sand that extend kilometres inland tsunamis. Stratigraphic series extensive sheets, intercalated dated volcanic-ash layers, show such unusually large occurred about every 500 years average 2,000-7,000 years, most recently 350 ago. Numerical simulations are best explained by individually multiple trench. We multi-segment persistently recur among number single-segment events.